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NORMAL LABORATORY VALUES

A Complete Clinical and Diagnostic Guide

Introduction

Laboratory investigations form the backbone of modern clinical medicine. Whether diagnosing anemia, evaluating kidney failure, managing diabetes, or monitoring infections, physicians rely heavily on laboratory data to make informed clinical decisions.

Understanding normal laboratory values is not simply about memorizing numbers. It involves:

Understanding the physiology behind each parameter
Knowing variations according to age and gender
Interpreting abnormal patterns
Recognizing clinical correlations

Normal values serve as reference ranges, which are statistically determined limits obtained from healthy populations. However, interpretation always depends on the clinical context.

In this article, we will systematically explore:

Hematological values
Biochemical parameters
Electrolytes
Liver function tests
Renal function tests
Lipid profile
Endocrine tests
Coagulation profile
Arterial blood gases
Urine examination
Special tests

SECTION 1: HEMATOLOGY

1. Complete Blood Count (CBC)

A Complete Blood Count is one of the most frequently ordered investigations worldwide. It evaluates blood cells and helps detect:

Anemia
Infection
Leukemia
Bleeding disorders
Inflammatory diseases

1. Hemoglobin (Hb)

Normal Values:

Adult Male: 13.5 – 17.5 g/dL
Adult Female: 12 – 15.5 g/dL
Children: 11 – 16 g/dL
Newborn: 14 – 24 g/dL

Clinical Significance

Hemoglobin is the oxygen-carrying protein in red blood cells.

Low hemoglobin indicates:

Iron deficiency anemia
Chronic disease
Blood loss
Bone marrow suppression

High hemoglobin may be seen in:

Polycythemia vera
Chronic hypoxia
Dehydration

2. Red Blood Cell Count (RBC)

Normal Values:

Male: 4.7 – 6.1 million/µL
Female: 4.2 – 5.4 million/µL

RBC count reflects bone marrow activity and oxygen transport capacity.

Low RBC:

Nutritional anemia
Bone marrow failure

High RBC:

Polycythemia
High altitude adaptation

3. Hematocrit (HCT / PCV)

Normal Values:

Male: 41 – 53%
Female: 36 – 46%

Hematocrit represents the percentage of blood volume occupied by red cells.

4. White Blood Cell Count (WBC)

Normal Range: 4,000 – 11,000 /µL

WBCs protect against infections.

High WBC (Leukocytosis):

Bacterial infections
Leukemia
Stress

Low WBC (Leukopenia):

Viral infections
Bone marrow suppression
Chemotherapy

5. Differential Leukocyte Count (DLC)

Cell Type	Normal %
Neutrophils	40–70%
Lymphocytes	20–40%
Monocytes	2–8%
Eosinophils	1–4%
Basophils	0–1%

Clinical Interpretation

Neutrophilia:

Bacterial infection
Acute inflammation

Lymphocytosis:

Viral infection
Tuberculosis

Eosinophilia:

Allergy
Parasitic infection
Asthma

6. Platelet Count

Normal Range:
150,000 – 450,000 /µL

Low platelets (Thrombocytopenia):

Dengue
ITP
Bone marrow failure

High platelets (Thrombocytosis):

Inflammation
Myeloproliferative disorders

SECTION 2: RED CELL INDICES

These indices help classify anemia.

1. Mean Corpuscular Volume (MCV)

Normal: 80 – 100 fL

Low MCV → Microcytic anemia (Iron deficiency)
High MCV → Macrocytic anemia (Vitamin B12 deficiency)

2. Mean Corpuscular Hemoglobin (MCH)

Normal: 27 – 33 pg

3. Mean Corpuscular Hemoglobin Concentration (MCHC)

Normal: 32 – 36 g/dL

Low MCHC indicates hypochromic anemia.

SECTION 3: RENAL FUNCTION TESTS (RFTs)

Kidney function is assessed using biochemical parameters.

1. Serum Creatinine

Normal:

Male: 0.7 – 1.3 mg/dL
Female: 0.6 – 1.1 mg/dL

Creatinine reflects glomerular filtration rate (GFR).

Increased in:

Acute kidney injury
Chronic kidney disease
Dehydration

2. Blood Urea Nitrogen (BUN)

Normal: 7 – 20 mg/dL

Elevated in:

Renal failure
Dehydration
High protein diet

3. Estimated GFR (eGFR)

Normal: >90 mL/min

Stages of CKD:

Stage 1: ≥90
Stage 2: 60–89
Stage 3: 30–59
Stage 4: 15–29
Stage 5: <15

SECTION 4: ELECTROLYTES

Electrolytes maintain fluid balance, nerve conduction, and muscle function.

1. Sodium (Na⁺)

Normal: 135 – 145 mEq/L

Low Sodium (Hyponatremia):

SIADH
Heart failure
Diuretics

High Sodium (Hypernatremia):

Dehydration
Diabetes insipidus

2. Potassium (K⁺)

Normal: 3.5 – 5.0 mEq/L

Low Potassium:

Vomiting
Diuretics
Diarrhea

High Potassium:

Renal failure
ACE inhibitors
Hemolysis

3. Chloride (Cl⁻)

Normal: 98 – 106 mEq/L

4. Bicarbonate (HCO₃⁻)

Normal: 22 – 28 mEq/L

Low in metabolic acidosis
High in metabolic alkalosis

SECTION 5: LIVER FUNCTION TESTS (LFTs)

Liver enzymes indicate hepatocellular damage or cholestasis.

1. ALT (SGPT)

Normal: 7 – 56 U/L

Elevated in:

Viral hepatitis
Drug-induced liver injury

2. AST (SGOT)

Normal: 10 – 40 U/L

Also elevated in muscle injury.

3. Alkaline Phosphatase (ALP)

Normal: 44 – 147 IU/L

Raised in:

Obstructive jaundice
Bone disease

4. Total Bilirubin

Normal: 0.1 – 1.2 mg/dL

High bilirubin causes jaundice.

SECTION 6: BLOOD GLUCOSE VALUES

Fasting Blood Glucose: 70 – 99 mg/dL

Prediabetes: 100 – 125 mg/dL

Diabetes: ≥126 mg/dL

Random Blood Glucose: <140 mg/dL normal

HbA1c

Normal: <5.7%
Prediabetes: 5.7–6.4%
Diabetes: ≥6.5%

SECTION 7: LIPID PROFILE

Total Cholesterol: <200 mg/dL

LDL: <100 mg/dL optimal

HDL:

40 mg/dL (men)
50 mg/dL (women)

Triglycerides: <150 mg/dL

SECTION 8: COAGULATION PROFILE

The coagulation system maintains a balance between bleeding and thrombosis.

1. Prothrombin Time (PT)

Normal: 11 – 13.5 seconds

PT evaluates the extrinsic pathway (Factors I, II, V, VII, X).

Prolonged PT seen in:

Liver disease
Vitamin K deficiency
Warfarin therapy
Disseminated intravascular coagulation (DIC)

2. International Normalized Ratio (INR)

Normal: 0.8 – 1.2
Therapeutic (Warfarin): 2 – 3

Used to monitor anticoagulation therapy.

3. Activated Partial Thromboplastin Time (aPTT)

Normal: 25 – 35 seconds

Evaluates intrinsic pathway.

Prolonged in:

Hemophilia
Heparin therapy
DIC

4. Bleeding Time

Normal: 2 – 7 minutes

Assesses platelet function.

SECTION 9: THYROID FUNCTION TESTS (TFTs)

Thyroid hormones regulate metabolism.

1. Thyroid Stimulating Hormone (TSH)

Normal: 0.4 – 4.0 mIU/L

High TSH → Hypothyroidism
Low TSH → Hyperthyroidism

2. Free T4

Normal: 0.8 – 1.8 ng/dL

3. Free T3

Normal: 2.3 – 4.2 pg/mL

Interpretation Pattern

Condition	TSH	T3/T4
Primary Hypothyroidism	↑	↓
Primary Hyperthyroidism	↓	↑
Subclinical Hypothyroidism	↑	Normal

SECTION 10: CARDIAC MARKERS

Used in diagnosing myocardial infarction.

1. Troponin I / T

Normal: <0.04 ng/mL

Highly specific for cardiac injury.
Rises within 3–6 hours after MI.

2. CK-MB

Normal: <5 ng/mL

Elevated in acute MI.

3. BNP (Brain Natriuretic Peptide)

Normal: <100 pg/mL

Elevated in:

Heart failure

SECTION 11: PANCREATIC ENZYMES

1. Serum Amylase

Normal: 30 – 110 U/L

Elevated in:

Acute pancreatitis
Salivary gland disorders

2. Serum Lipase

Normal: 0 – 160 U/L

More specific for pancreatitis.

SECTION 12: ARTERIAL BLOOD GAS (ABG)

ABG evaluates acid-base balance.

Normal ABG Values

Parameter	Normal Value
pH	7.35 – 7.45
PaCO₂	35 – 45 mmHg
PaO₂	80 – 100 mmHg
HCO₃⁻	22 – 26 mEq/L
O₂ Saturation	95 – 100%

Acid-Base Disorders

Metabolic Acidosis:

Low pH
Low HCO₃⁻

Respiratory Acidosis:

Low pH
High PaCO₂

Metabolic Alkalosis:

High pH
High HCO₃⁻

Respiratory Alkalosis:

High pH
Low PaCO₂

SECTION 13: URINALYSIS

Urine examination provides important diagnostic clues.

1. Physical Examination

Color: Pale yellow
Specific Gravity: 1.005 – 1.030

2. Chemical Examination

Parameter	Normal
Protein	Negative
Glucose	Negative
Ketones	Negative
Blood	Negative
Nitrite	Negative

3. Microscopy

RBC: 0 – 2 /HPF
WBC: 0 – 5 /HPF
Casts: None

SECTION 14: INFLAMMATORY MARKERS

1. ESR (Erythrocyte Sedimentation Rate)

Men: 0 – 15 mm/hr
Women: 0 – 20 mm/hr

Elevated in:

Tuberculosis
Autoimmune diseases
Infections

2. C-Reactive Protein (CRP)

Normal: <3 mg/L

Increased in:

Acute inflammation
Sepsis

SECTION 15: SERUM PROTEINS

1. Total Protein

Normal: 6 – 8 g/dL

2. Albumin

Normal: 3.5 – 5.0 g/dL

Low in:

Liver disease
Nephrotic syndrome

3. Globulin

Normal: 2.0 – 3.5 g/dL

SECTION 16: CALCIUM & BONE PROFILE

1. Serum Calcium

Normal: 8.5 – 10.5 mg/dL

Low in:

Hypoparathyroidism
Vitamin D deficiency

High in:

Hyperparathyroidism
Malignancy

2. Serum Phosphate

Normal: 2.5 – 4.5 mg/dL

3. Vitamin D (25-OH)

Normal: 20 – 50 ng/mL

SECTION 17: MAGNESIUM

Normal: 1.7 – 2.2 mg/dL

Low magnesium:

Chronic alcoholism
Diuretics

High magnesium:

Renal failure

SECTION 18: TUMOR MARKERS

Tumor markers are substances produced by cancer cells or by the body in response to cancer. They are useful for monitoring treatment and recurrence rather than for primary diagnosis.

1. Alpha-Fetoprotein (AFP)

Normal: <10 ng/mL

Elevated in:

Hepatocellular carcinoma
Germ cell tumors

Also elevated in pregnancy.

2. Carcinoembryonic Antigen (CEA)

Normal: <3 ng/mL (non-smoker)
<5 ng/mL (smoker)

Elevated in:

Colorectal carcinoma
Pancreatic cancer
Gastric carcinoma

3. Prostate-Specific Antigen (PSA)

Normal: <4 ng/mL

Elevated in:

Prostate cancer
Benign prostatic hyperplasia
Prostatitis

4. CA-125

Normal: <35 U/mL

Elevated in:

Ovarian carcinoma
Endometriosis

5. CA 19-9

Normal: <37 U/mL

Elevated in:

Pancreatic carcinoma
Biliary tract cancers

SECTION 19: HORMONAL ASSAYS

1. Serum Cortisol

Morning: 5 – 25 µg/dL

Low in:

Addison’s disease

High in:

Cushing’s syndrome

2. Prolactin

Male: 2 – 18 ng/mL
Female: 2 – 29 ng/mL

Elevated in:

Prolactinoma
Hypothyroidism

3. LH (Luteinizing Hormone)

Men: 1.8 – 8.6 IU/L
Women: varies by menstrual cycle

4. FSH (Follicle Stimulating Hormone)

Men: 1.5 – 12.4 IU/L
Women: cycle dependent

5. Testosterone

Male: 300 – 1000 ng/dL
Female: 15 – 70 ng/dL

6. Estradiol

Women (follicular phase): 30 – 120 pg/mL

SECTION 20: IRON STUDIES

Iron profile helps diagnose anemia type.

1. Serum Iron

Normal: 60 – 170 µg/dL

2. Ferritin

Male: 30 – 400 ng/mL
Female: 15 – 150 ng/mL

Low ferritin indicates iron deficiency.

3. Total Iron Binding Capacity (TIBC)

Normal: 240 – 450 µg/dL

Increased in iron deficiency.

4. Transferrin Saturation

Normal: 20 – 50%

SECTION 21: VITAMIN LEVELS

Vitamin B12

Normal: 200 – 900 pg/mL

Low in:

Pernicious anemia
Malabsorption

Folate

Normal: 2 – 20 ng/mL

Vitamin D (25-OH)

Normal: 20 – 50 ng/mL

Deficiency: <20 ng/mL

SECTION 22: CEREBROSPINAL FLUID (CSF) ANALYSIS

Normal CSF:

Parameter	Normal Value
Appearance	Clear
Opening Pressure	10–20 cm H₂O
Protein	15–45 mg/dL
Glucose	45–80 mg/dL
WBC	0–5 cells/µL

Interpretation Patterns

Bacterial Meningitis:

High protein
Low glucose
High neutrophils

Viral Meningitis:

Normal glucose
Mild protein increase
Lymphocytes predominant

SECTION 23: PLEURAL FLUID ANALYSIS

Normal pleural fluid is minimal.

Key parameters:

Protein
LDH
Glucose
Cell count

Light’s Criteria (for exudate):

Pleural protein / Serum protein >0.5
Pleural LDH / Serum LDH >0.6

SECTION 24: ASCITIC FLUID

Serum Ascites Albumin Gradient (SAAG):

SAAG ≥1.1 → Portal hypertension
SAAG <1.1 → Non-portal causes

SECTION 25: SYNOVIAL FLUID

Normal:

Clear
Viscous
WBC <200 cells/µL

Septic arthritis:

WBC >50,000
Neutrophil predominance

SECTION 26: PEDIATRIC NORMAL VALUES

Children differ significantly from adults.

Newborn:

Higher hemoglobin (14–24 g/dL)
Higher bilirubin

Children:

Higher alkaline phosphatase (bone growth)

SECTION 27: PREGNANCY-SPECIFIC LAB CHANGES

Pregnancy causes physiological alterations.

Hemoglobin:

Slightly decreased (hemodilution)

WBC:

Mild leukocytosis

Alkaline Phosphatase:

Elevated (placental production)

D-dimer:

Elevated physiologically

SECTION 28: CRITICAL ICU VALUES

Potassium:

<2.5 or >6.5 mEq/L is life-threatening

Sodium:

<120 or >160 mEq/L dangerous

pH:

<7.1 or >7.6 critical

Glucose:

<40 mg/dL severe hypoglycemia

QUICK REVISION MNEMONICS

Hyperkalemia ECG changes: "Peaked T waves first"

Microcytic anemia causes: "TICS"

Thalassemia
Iron deficiency
Chronic disease
Sideroblastic

SECTION 29: PATTERN-BASED INTERPRETATION OF LAB VALUES

Medicine is about recognizing patterns rather than isolated numbers.

1. Pattern: Microcytic Anemia

Lab Findings:

↓ Hemoglobin
↓ MCV (<80 fL)
↓ MCHC
↑ RDW (sometimes)

Common Causes:

Iron deficiency anemia
Thalassemia
Anemia of chronic disease
Sideroblastic anemia

Key Differentiation:

Parameter	Iron Deficiency	Thalassemia
Ferritin	↓	Normal
TIBC	↑	Normal
RBC count	↓	Normal/↑

Clinical Tip:
Low ferritin is almost diagnostic of iron deficiency.

2. Pattern: Obstructive Jaundice

Lab Findings:

↑ Direct (conjugated) bilirubin
↑ Alkaline phosphatase
Mild ↑ AST/ALT

Common Causes:

Gallstones
Pancreatic head tumor
Biliary obstruction

Clinical Clue: Dark urine + Pale stool + Itching

3. Pattern: Hepatocellular Injury

Lab Findings:

Marked ↑ ALT
Marked ↑ AST
Mild ↑ ALP

Common Causes:

Viral hepatitis
Drug-induced injury
Alcoholic hepatitis

AST:ALT >2 suggests alcoholic liver disease.

4. Pattern: Acute Kidney Injury (AKI)

Lab Findings:

↑ Creatinine
↑ BUN
Electrolyte imbalance

BUN/Creatinine ratio:

20:1 → Prerenal cause
<15:1 → Intrinsic renal damage

5. Pattern: Diabetic Ketoacidosis (DKA)

Lab Findings:

↑ Glucose
↓ pH (<7.3)
↓ HCO₃⁻
Positive ketones
↑ Anion gap

Anion Gap Formula: Na⁺ − (Cl⁻ + HCO₃⁻)
Normal: 8–12 mEq/L

SECTION 30: CASE-BASED LAB INTERPRETATION

Case 1

Patient: 25-year-old female with fatigue.

Labs: Hb 8 g/dL
MCV 70 fL
Ferritin 8 ng/mL

Diagnosis: Iron deficiency anemia

Reason: Microcytic anemia + low ferritin.

Case 2

Patient: 60-year-old male, chest pain.

Labs: Troponin elevated
CK-MB elevated

Diagnosis: Acute myocardial infarction

Case 3

Patient: Alcoholic patient with jaundice.

Labs: AST 200
ALT 80

AST:ALT >2
Likely alcoholic hepatitis.

Case 4

Patient: Dehydrated elderly.

Labs: Na⁺ 152 mEq/L
High serum osmolality

Diagnosis: Hypernatremia due to dehydration.

SECTION 31: DRUG EFFECTS ON LAB VALUES

Many medications alter laboratory parameters.

1. ACE Inhibitors

May increase:

Potassium
Creatinine

2. Warfarin

Increases:

3. Heparin

Prolongs:

aPTT

4. Statins

May increase:

Liver enzymes
CK

5. Oral Contraceptives

May increase:

Clotting factors
Triglycerides

SECTION 32: EMERGENCY LAB VALUES

These values require urgent action.

Potassium:

<2.5 or >6.5 mEq/L

Sodium:

<120 or >160 mEq/L

Glucose:

<40 mg/dL
500 mg/dL

pH:

<7.1 severe acidosis
7.6 severe alkalosis

Troponin:

Any significant rise with symptoms

SECTION 33: COMMON LAB PITFALLS

1. Hemolysis

False increase in:

Potassium
LDH
AST

2. Dehydration

May falsely elevate:

Hemoglobin
Hematocrit
Urea

3. Lab Timing Errors

Cortisol:

Must be measured in morning

Glucose:

Fasting required for accuracy

4. Pregnancy Changes

Mild:

Anemia
Leukocytosis
Elevated ALP

These are physiological, not pathological.

SECTION 34: HIGH-YIELD EXAM TABLE

Parameter	Normal	High Indicates	Low Indicates
Hb	12–17 g/dL	Polycythemia	Anemia
WBC	4–11k	Infection	Viral / marrow failure
Platelets	150–450k	Inflammation	Dengue / ITP
Creatinine	0.6–1.3	Renal failure	Low muscle mass
ALT	7–56	Hepatitis	—
TSH	0.4–4	Hypothyroid	Hyperthyroid
Sodium	135–145	Dehydration	SIADH
Potassium	3.5–5	Renal failure	Diuretics

SECTION 35: RAPID REVISION MNEMONICS

Causes of Hypercalcemia: "CHIMPANZEES"

Calcium excess
Hyperparathyroidism
Immobilization
Malignancy
Paget
Addison
Neoplasm
Zollinger-Ellison
Excess Vitamin D
Sarcoidosis

ABG Quick Rule: ROME Respiratory Opposite
Metabolic Equal

SECTION 36: HOW TO STUDY NORMAL LAB VALUES EFFECTIVELY

Do not memorize blindly
Learn with physiology
Study patterns
Practice case scenarios
Use mnemonics
Revise frequently

SECTION 37: ADVANCED ENDOCRINE PANELS

1. Parathyroid Hormone (PTH)

Normal: 10 – 65 pg/mL

High PTH:

Primary hyperparathyroidism
Chronic kidney disease
Vitamin D deficiency

Low PTH:

Hypoparathyroidism
Post-thyroid surgery

Clinical Pattern:

Calcium	PTH	Diagnosis
↑ Ca	↑ PTH	Primary hyperparathyroidism
↑ Ca	↓ PTH	Malignancy
↓ Ca	↑ PTH	Secondary hyperparathyroidism

2. Adrenocorticotropic Hormone (ACTH)

Normal: 7 – 63 pg/mL

High ACTH:

Cushing disease
Ectopic ACTH production

Low ACTH:

Adrenal adenoma

3. Aldosterone

Normal (upright): 4 – 31 ng/dL

High in:

Conn’s syndrome
Secondary hyperaldosteronism

4. Renin Activity

Normal: 0.6 – 4.3 ng/mL/hr

Used with aldosterone to diagnose primary hyperaldosteronism.

5. Insulin (Fasting)

Normal: 2 – 25 µIU/mL

Elevated in:

Insulinoma
Insulin resistance

SECTION 38: AUTOIMMUNE MARKERS

1. ANA (Antinuclear Antibody)

Normal: Negative

Positive in:

Systemic lupus erythematosus (SLE)
Autoimmune hepatitis
Sjögren syndrome

2. Anti-dsDNA

Normal: Negative

Specific for:

3. Rheumatoid Factor (RF)

Normal: <20 IU/mL

Elevated in:

Rheumatoid arthritis

4. Anti-CCP

More specific for rheumatoid arthritis.

5. ANCA

c-ANCA:

Granulomatosis with polyangiitis

p-ANCA:

Microscopic polyangiitis

SECTION 39: INFECTIOUS DISEASE MARKERS

1. Procalcitonin

Normal: <0.1 ng/mL

Elevated in:

Bacterial sepsis

Helps differentiate bacterial from viral infections.

2. D-Dimer

Normal: <0.5 µg/mL

Elevated in:

Pulmonary embolism
DVT
DIC

Note: Also elevated in pregnancy.

3. CRP (High Sensitivity)

Normal: <3 mg/L

Used for:

Cardiovascular risk assessment

4. HIV ELISA

Normal: Non-reactive

5. HBsAg

Normal: Negative

Positive indicates hepatitis B infection.

SECTION 40: TOXICOLOGY LEVELS

1. Paracetamol (Acetaminophen)

Therapeutic: 10 – 30 µg/mL

Toxic:

150 µg/mL at 4 hours post ingestion

2. Lithium

Therapeutic: 0.6 – 1.2 mEq/L

Toxic: >1.5 mEq/L

3. Digoxin

Therapeutic: 0.5 – 2.0 ng/mL

Toxic: >2.0 ng/mL

4. Theophylline

Therapeutic: 10 – 20 µg/mL

Toxic: >20 µg/mL

SECTION 41: NEONATAL ICU VALUES

Newborns have distinct physiological ranges.

Hemoglobin: 14 – 24 g/dL

Bilirubin: Higher due to physiological jaundice

Glucose:

45 mg/dL normal in neonates

Calcium: 8 – 10 mg/dL

SECTION 42: GERIATRIC LAB VARIATIONS

Elderly patients may have:

Slightly lower hemoglobin
Reduced renal function (higher creatinine even at mild disease)
Lower albumin
Increased ESR

Clinical pearl:
Always interpret renal function using eGFR, not just creatinine.

SECTION 43: CRITICAL DIFFERENTIAL PATTERNS

High Anion Gap Metabolic Acidosis

Mnemonic: MUDPILES

Methanol
Uremia
DKA
Propylene glycol
Infection (lactic acidosis)
Lactic acidosis
Ethylene glycol
Salicylates

Low Anion Gap Causes

Hypoalbuminemia
Multiple myeloma

SECTION 44: VIVA EXAM CLINICAL PEARLS

ALT is more liver-specific than AST.
Troponin remains elevated for 7–10 days after MI.
Ferritin is an acute-phase reactant.
Albumin reflects chronic nutritional status.
ESR rises slowly; CRP rises rapidly.
ALP is elevated in pregnancy (placental source).
Potassium changes affect ECG immediately.

SECTION 45: RAPID ICU ALERT TABLE

Parameter	Danger Level
Potassium	>6.5 or <2.5
Sodium	<120 or >160
Glucose	<40 or >500
pH	<7.1
Calcium	<7 mg/dL
Troponin	Any significant rise

SECTION 46: LAB INTERPRETATION ALGORITHMS

1. Approach to Anemia

Step 1: Check Hemoglobin
↓ Hb = Anemia

Step 2: Check MCV

MCV <80 → Microcytic
MCV 80–100 → Normocytic
MCV >100 → Macrocytic

Step 3: Further Evaluation

Microcytic → Ferritin
Normocytic → Reticulocyte count
Macrocytic → Vitamin B12 / Folate

2. Approach to Jaundice

Step 1: Check Bilirubin
Step 2: Direct vs Indirect

Indirect ↑ → Hemolysis
Direct ↑ → Obstruction

Step 3: Check ALP

High ALP → Obstructive pattern
High ALT/AST → Hepatocellular

3. Approach to Hyponatremia

Step 1: Check serum osmolality
Step 2: Assess volume status

Hypovolemic → Vomiting, diarrhea
Euvolemic → SIADH
Hypervolemic → Heart failure

4. Approach to Hyperkalemia

Step 1: Confirm sample not hemolyzed
Step 2: Check ECG
Step 3: Identify cause

Renal failure
ACE inhibitors
DKA

Emergency if >6.5 mEq/L.

SECTION 47: RAPID REVISION MASTER TABLE

Test	Normal Value
Hb	12–17 g/dL
WBC	4–11 ×10³/µL
Platelets	150–450 ×10³/µL
Sodium	135–145 mEq/L
Potassium	3.5–5.0 mEq/L
Creatinine	0.6–1.3 mg/dL
ALT	7–56 U/L
Bilirubin	0.1–1.2 mg/dL
TSH	0.4–4.0 mIU/L
Glucose (Fasting)	70–99 mg/dL
Calcium	8.5–10.5 mg/dL
ABG pH	7.35–7.45

SECTION 48: HIGH-YIELD EXAM QUESTIONS (WITH ANSWERS)

Q1:

Patient has Hb 9 g/dL and MCV 68 fL. Most likely cause?
Answer: Iron deficiency anemia.

Q2:

Troponin rises after how many hours of MI?
Answer: 3–6 hours.

Q3:

TSH high, T4 low. Diagnosis?
Answer: Primary hypothyroidism.

Q4:

Which lab test is most specific for pancreatitis?
Answer: Serum lipase.

Q5:

AST:ALT >2 suggests?
Answer: Alcoholic liver disease.

Q6:

Ferritin low indicates?
Answer: Iron deficiency.

Q7:

High ALP with normal ALT suggests?
Answer: Obstructive jaundice or bone disease.

Q8:

D-dimer is used to rule out?
Answer: Pulmonary embolism / DVT.

Q9:

Most sensitive marker for MI?
Answer: Troponin.

Q10:

Normal anion gap?
Answer: 8–12 mEq/L.

SECTION 49: CLINICAL FLOWCHART – METABOLIC ACIDOSIS

Step 1: Check pH
If <7.35 → Acidosis

Step 2: Check HCO₃⁻
Low → Metabolic

Step 3: Calculate Anion Gap

High gap → DKA, lactic acidosis
Normal gap → Diarrhea, renal tubular acidosis

SECTION 50: COMMON LAB TRAPS IN EXAMS

ESR rises slowly; CRP rises quickly
Ferritin increases in inflammation
Creatinine may be normal in early renal failure
Pregnancy lowers hemoglobin
Hemolysis falsely elevates potassium
Albumin decreases in chronic liver disease

SECTION 51: 20-MINUTE ULTRA-FAST REVISION GUIDE

If exam tomorrow, revise:

Hematology: Hb, MCV, Platelets

Electrolytes: Na, K, Ca

Renal: Creatinine, BUN

Liver: ALT, AST, ALP, Bilirubin

Endocrine: TSH, T4

Cardiac: Troponin

ABG: pH, PaCO₂, HCO₃⁻

Glucose: Fasting, HbA1c

SECTION 52: GOLDEN CLINICAL RULES

Always interpret labs with clinical context.
One abnormal value does not confirm diagnosis.
Trends are more important than single readings.
Consider lab error before panic.
Always correlate with patient symptoms.

SECTION 53: LAB PROFILE IN SEPSIS

Sepsis produces characteristic laboratory changes.

Typical Findings:

↑ WBC (or sometimes low in severe sepsis)
↑ CRP
↑ Procalcitonin
↑ Lactate (>2 mmol/L concerning)
↑ Creatinine (renal involvement)
↑ Bilirubin (liver involvement)
↓ Platelets (sepsis-induced DIC)

Key Marker:
Serum Lactate

Normal: 0.5 – 1 mmol/L

2 mmol/L → Tissue hypoperfusion
4 mmol/L → Severe sepsis

Clinical pearl:
Lactate clearance predicts survival.

SECTION 54: LAB PROFILE IN SHOCK

1. Hypovolemic Shock

Labs:

↑ Hemoglobin (hemoconcentration early)
↑ Urea
↑ Creatinine
Metabolic acidosis

2. Cardiogenic Shock

Labs:

↑ Troponin
↑ BNP
↑ Lactate

3. Septic Shock

Labs:

↑ Lactate
↑ Procalcitonin
↓ Platelets

SECTION 55: MULTI-ORGAN DYSFUNCTION SYNDROME (MODS)

Lab pattern shows failure of multiple systems.

Renal:

↑ Creatinine

Liver:

↑ Bilirubin
↑ INR

Hematologic:

↓ Platelets
↑ PT

Respiratory:

↓ PaO₂

Metabolic:

Severe acidosis

SECTION 56: ELECTROLYTE CORRECTION PRINCIPLES

Sodium Correction Rule

Correct slowly.

Maximum correction: 8–10 mEq/L per 24 hours

Rapid correction risks: Osmotic demyelination syndrome.

Potassium Correction

IV potassium: Not more than 10–20 mEq/hr

Always monitor ECG.

Calcium Correction Formula

Corrected Calcium =
Measured Ca + 0.8 (4 − Albumin)

Used when albumin is low.

SECTION 57: TRANSFUSION-RELATED LAB CHANGES

After blood transfusion:

↑ Hemoglobin
↑ Potassium (stored blood effect)
↑ Iron

Massive transfusion may cause:

Hypocalcemia
Dilutional coagulopathy

SECTION 58: NUTRITIONAL STATUS MARKERS

Albumin

Normal: 3.5 – 5 g/dL

Low in chronic malnutrition.

Prealbumin

More sensitive marker for short-term nutrition.

Total Lymphocyte Count

Low in protein malnutrition.

SECTION 59: DRUG THERAPEUTIC MONITORING – ADVANCED

Vancomycin

Trough level: 10 – 20 µg/mL

High levels → Nephrotoxicity

Phenytoin

Therapeutic: 10 – 20 µg/mL

Toxic:

20 µg/mL

Valproate

Therapeutic: 50 – 100 µg/mL

SECTION 60: LAB PATTERNS IN COMMON CONDITIONS

1. Nephrotic Syndrome

↓ Albumin
↑ Cholesterol
Proteinuria

2. Hemolytic Anemia

↓ Hemoglobin
↑ LDH
↑ Indirect bilirubin
↓ Haptoglobin

3. Acute Pancreatitis

↑ Lipase
↑ Amylase
Hypocalcemia (severe cases)

4. Hyperthyroidism

↓ TSH
↑ T3/T4

5. Hypothyroidism

↑ TSH
↓ T4

SECTION 61: CRITICAL LAB VALUES IN EMERGENCY MEDICINE

Immediate Action Required If:

Potassium >6.5
Sodium <120
Glucose <40
Calcium <7
pH <7.1
INR >5 (bleeding risk)

SECTION 62: COMMON LAB CONFUSIONS IN STUDENTS

ALT is more liver-specific than AST
CK-MB rises earlier than troponin but is less specific
ALP high in bone growth
Ferritin increases in inflammation
D-dimer is sensitive but not specific

SECTION 63: ADVANCED ACID-BASE INTERPRETATION

Winter’s Formula:

Expected PaCO₂ =
(1.5 × HCO₃⁻) + 8 ± 2

Used in metabolic acidosis to check respiratory compensation.

SECTION 64: CLINICAL INTEGRATION EXAMPLE

Patient: 65-year-old diabetic with fever and confusion.

Labs: WBC 18,000
Creatinine 2.5
Lactate 5
Platelets 90,000

Interpretation: Septic shock with multiorgan dysfunction.

SECTION 66: HOW ARE NORMAL LAB VALUES DETERMINED?

Normal values are not “fixed numbers.”
They are reference ranges.

Reference range = Mean ± 2 standard deviations
This includes 95% of healthy individuals.

Important Concept:

5% of healthy people will naturally fall outside the “normal” range.

That does NOT automatically mean disease.

SECTION 67: BIOLOGICAL VARIATION

Lab values vary due to:

Age
Gender
Ethnicity
Altitude
Diet
Circadian rhythm
Pregnancy
Hydration

Example:

Cortisol: Highest in morning
Lowest at midnight

Hemoglobin: Higher at high altitude

Creatinine: Higher in muscular individuals

SECTION 68: SENSITIVITY VS SPECIFICITY

Understanding this is crucial for lab interpretation.

Sensitivity: Ability to detect disease when present.

Specificity: Ability to exclude disease when absent.

Example:

D-dimer: Highly sensitive
Not specific

Troponin: Highly specific for cardiac injury

SECTION 69: POSITIVE AND NEGATIVE PREDICTIVE VALUE

Depends on disease prevalence.

In low-prevalence settings: More false positives occur.

Clinical lesson: Never interpret lab values without considering patient population.

SECTION 70: PRE-ANALYTICAL ERRORS

Most lab errors occur before testing.

Examples:

Wrong sample collection
Improper storage
Delayed processing
Hemolysis
Incorrect labeling

Example: Hemolyzed sample → false high potassium.

SECTION 71: ANALYTICAL ERRORS

Machine calibration errors
Reagent issues
Technical malfunction

Laboratories use:

Internal quality control
External quality assurance programs

SECTION 72: POST-ANALYTICAL ERRORS

Reporting mistakes
Data entry errors
Misinterpretation

Clinical rule: If lab result does not match clinical picture → Repeat test.

SECTION 73: HIGH-SENSITIVITY MARKERS

High-Sensitivity Troponin

Detects very small myocardial injury.

Used for early MI detection.

High-Sensitivity CRP (hs-CRP)

Cardiovascular risk:

<1 mg/L → Low risk
1–3 mg/L → Moderate

3 mg/L → High risk

SECTION 74: ADVANCED CARDIAC BIOMARKERS

BNP
NT-proBNP
Myoglobin
CK-MB

BNP interpretation:

<100 → Unlikely heart failure

400 → Likely heart failure

SECTION 75: ADVANCED RENAL BIOMARKERS

Cystatin C

More sensitive than creatinine in early kidney disease.

NGAL (Neutrophil Gelatinase-Associated Lipocalin)

Early marker of acute kidney injury.

SECTION 76: INFLAMMATORY CYTOKINES

IL-6
TNF-alpha

Used in research and severe infections.

SECTION 77: COAGULATION ADVANCES

D-dimer
Fibrinogen
Anti-Xa level

Anti-Xa: Monitors low molecular weight heparin.

SECTION 78: LAB VALUES IN EVIDENCE-BASED MEDICINE

Single abnormal lab value rarely confirms diagnosis.

Diagnosis requires:

Clinical probability
Lab result
Imaging
Response to therapy

Example:

Elevated troponin + chest pain + ECG changes → MI
Troponin alone → Not sufficient.

SECTION 79: LAB TRENDING PRINCIPLE

One reading = Snapshot
Multiple readings = Story

Trend is more important than single abnormal result.

Example:

Creatinine rising daily → Acute kidney injury
Stable mild elevation → Chronic kidney disease

SECTION 80: REFERENCE RANGE LIMITATIONS

Reference ranges differ between labs due to:

Methodology
Population differences
Calibration

Always interpret using lab-specific reference.

SECTION 81: INTERFERENCE IN LAB TESTS

Drugs
Biotin supplements
Hemolysis
Lipemia
Hyperbilirubinemia

Example:

High-dose biotin interferes with thyroid assays.

SECTION 82: LAB VALUES IN RESEARCH

Used to:

Measure treatment response
Monitor toxicity
Evaluate disease progression
Determine prognosis

Example:

CRP reduction in inflammatory disease
HbA1c reduction in diabetes trials

SECTION 83: ETHICAL LAB PRACTICE

Avoid unnecessary testing.
Avoid over-interpretation.
Avoid defensive medicine.

Remember:

Every test has cost and implication.

SECTION 84: FINAL MASTER PRINCIPLES

Lab values support diagnosis; they do not replace it.
Interpret with history and examination.
Consider biological variation.
Repeat doubtful results.
Monitor trends.
Recognize emergency thresholds.
Understand limitations.

SECTION 85: HEMATOLOGY CASES

Case 1: Severe Fatigue

Hb: 7.5 g/dL
MCV: 68 fL
Ferritin: 6 ng/mL

Diagnosis: Iron deficiency anemia
Reason: Microcytic anemia + low ferritin.

Case 2: Young Male with Pallor

Hb: 10 g/dL
MCV: 65 fL
Ferritin: Normal
RBC count: High-normal

Diagnosis: Thalassemia trait
Clue: Normal ferritin + high RBC count.

Case 3: Elderly with Bone Pain

Hb: 9 g/dL
Calcium: 11.8 mg/dL
Creatinine: Elevated
ESR: High

Diagnosis: Multiple myeloma (suspected).

Case 4: Fever with Low Platelets

WBC: 4,000
Platelets: 60,000
Hb: Normal

Likely: Viral infection (e.g., dengue).

Case 5: Bleeding Gums

Platelets: 25,000
PT: Normal
aPTT: Normal

Diagnosis: Immune thrombocytopenic purpura (ITP).

SECTION 86: RENAL CASES

Case 6: Dehydrated Patient

Creatinine: 2.0
BUN: 60
Ratio >20

Diagnosis: Prerenal AKI.

Case 7: Diabetic Patient

Creatinine rising gradually
Proteinuria present

Diagnosis: Diabetic nephropathy.

Case 8: Metabolic Acidosis

pH: 7.25
HCO₃⁻: 14
Anion gap: 20

Likely: DKA or lactic acidosis.

SECTION 87: LIVER CASES

Case 9: Alcoholic Patient

AST: 180
ALT: 70

AST:ALT >2
Diagnosis: Alcoholic hepatitis.

Case 10: Obstructive Pattern

Bilirubin: 4
ALP: Very high
ALT: Mild increase

Diagnosis: Obstructive jaundice.

Case 11: Viral Hepatitis

ALT: 900
AST: 850

Diagnosis: Acute viral hepatitis.

SECTION 88: ENDOCRINE CASES

Case 12: Weight Gain & Fatigue

TSH: 8
T4: Low

Diagnosis: Primary hypothyroidism.

Case 13: Weight Loss & Palpitations

TSH: 0.01
T3/T4: High

Diagnosis: Hyperthyroidism.

Case 14: Hypercalcemia

Calcium: 11.5
PTH: High

Diagnosis: Primary hyperparathyroidism.

SECTION 89: CARDIAC CASES

Case 15: Chest Pain

Troponin elevated
CK-MB elevated

Diagnosis: Myocardial infarction.

Case 16: Breathlessness

BNP: 800

Diagnosis: Heart failure.

SECTION 90: ELECTROLYTE CASES

Case 17: Confusion

Sodium: 118

Diagnosis: Severe hyponatremia.

Case 18: Muscle Weakness

Potassium: 2.8

Diagnosis: Hypokalemia.

Case 19: ECG Changes

Potassium: 6.8

Diagnosis: Life-threatening hyperkalemia.

SECTION 91: ABG CASES

Case 20: COPD Patient

pH: 7.30
PaCO₂: High
HCO₃⁻: High

Diagnosis: Chronic respiratory acidosis with compensation.

Case 21: Anxiety Attack

pH: 7.48
PaCO₂: Low

Diagnosis: Respiratory alkalosis.

SECTION 92: INFECTIOUS CASES

Case 22: Septic Shock

WBC: 20,000
Lactate: 6
Platelets: Low

Diagnosis: Severe sepsis.

Case 23: Bacterial Infection

Procalcitonin elevated

Suggests bacterial cause.

SECTION 93: PANCREATIC CASES

Case 24: Severe Epigastric Pain

Lipase: High
Calcium: Low

Diagnosis: Acute pancreatitis.

SECTION 94: COAGULATION CASES

Case 25: On Warfarin

INR: 5

Risk: Bleeding.

Case 26: DIC

Platelets: Low
PT prolonged
D-dimer high

Diagnosis: Disseminated intravascular coagulation.

SECTION 95: NUTRITIONAL CASES

Case 27: Chronic Liver Disease

Albumin: 2.5

Indicates poor synthetic function.

Case 28: B12 Deficiency

MCV: 110
B12: Low

Diagnosis: Megaloblastic anemia.

SECTION 96: PEDIATRIC CASES

Case 29: Neonatal Jaundice

Bilirubin elevated
Other labs normal

Likely physiological jaundice.

SECTION 97: TOXICOLOGY CASES

Case 30: Paracetamol Overdose

Level >150 µg/mL

Risk: Hepatic necrosis.

Case 31: Lithium Toxicity

Level 2.0

Symptoms: Tremors, confusion.

SECTION 98: INTEGRATED ICU CASE

Case 32:

Elderly septic patient:

Creatinine ↑
Bilirubin ↑
Platelets ↓
Lactate ↑

Diagnosis: Multi-organ dysfunction syndrome.

SECTION 99: COMMON EXAM TRAPS

Normal creatinine does NOT exclude kidney disease.
Normal troponin early does NOT exclude MI.
Normal hemoglobin does NOT exclude acute bleeding (early).
Elevated ESR is non-specific.
D-dimer is sensitive but not diagnostic.

SECTION 101: RHEUMATOLOGY PANEL

Autoimmune diseases often require multiple laboratory markers.

1. Rheumatoid Arthritis Panel

Tests:

Rheumatoid Factor (RF)
Anti-CCP
ESR
CRP

Typical Findings:

RF positive
Anti-CCP positive (more specific)
Elevated ESR and CRP

Clinical Pearl: Anti-CCP predicts erosive disease.

2. Systemic Lupus Erythematosus (SLE)

Tests:

ANA
Anti-dsDNA
Anti-Smith
Complement levels (C3, C4)

Findings:

ANA positive
Anti-dsDNA elevated
Low complement (active disease)

3. Ankylosing Spondylitis

Test:

HLA-B27

Positive in many patients (not diagnostic alone).

SECTION 102: ONCOLOGY LAB PANEL

1. Multiple Myeloma

Labs:

Elevated total protein
Low albumin
High calcium
High creatinine
ESR elevated

Mnemonic: CRAB

Calcium
Renal failure
Anemia
Bone lesions

2. Leukemia

Findings:

Extremely high or low WBC
Abnormal peripheral smear
Low platelets

3. Tumor Lysis Syndrome

Labs:

Hyperkalemia
Hyperphosphatemia
Hyperuricemia
Hypocalcemia

Medical emergency.

SECTION 103: NEUROLOGY LAB PANEL

1. Guillain-Barré Syndrome

CSF:

High protein
Normal cell count

Called albuminocytologic dissociation.

2. Meningitis

Bacterial:

Low glucose
High protein
Neutrophils

Viral:

Normal glucose
Lymphocytes

3. Myasthenia Gravis

Test:

Anti-acetylcholine receptor antibodies.

SECTION 104: PULMONOLOGY LAB PANEL

1. Pulmonary Embolism

Test:

D-dimer elevated

Definitive diagnosis: Imaging required.

2. COPD

ABG:

Chronic respiratory acidosis
Compensated metabolic alkalosis

SECTION 105: GASTROENTEROLOGY PANEL

1. Celiac Disease

Test:

Anti-tTG antibodies

2. Inflammatory Bowel Disease

Labs:

Elevated CRP
Anemia
Low albumin

3. Pancreatitis Severity

Check:

Lipase
Calcium
Hematocrit
CRP

SECTION 106: ADVANCED HEMATOLOGY

1. Hemolytic Anemia Panel

Labs:

High LDH
High indirect bilirubin
Low haptoglobin
High reticulocyte count

2. Aplastic Anemia

Labs:

Low Hb
Low WBC
Low platelets

Pancytopenia.

3. Polycythemia Vera

Labs:

High Hb
Low EPO
JAK2 mutation positive

SECTION 107: NEPHROLOGY ADVANCED PANEL

1. Nephritic Syndrome

Labs:

Hematuria
RBC casts
Mild proteinuria

2. Nephrotic Syndrome

Labs:

Heavy proteinuria
Low albumin
High cholesterol

3. Renal Tubular Acidosis

Normal anion gap metabolic acidosis.

SECTION 108: ENDOCRINE ADVANCED PANEL

1. Cushing Syndrome

Labs:

High cortisol
Dexamethasone suppression test abnormal

2. Addison Disease

Labs:

Low cortisol
High ACTH
Low sodium
High potassium

3. Pheochromocytoma

Test:

Plasma metanephrines elevated.

SECTION 109: CRITICAL DIFFERENTIAL TABLE

Pattern	Most Likely Diagnosis
High AST>ALT	Alcoholic liver disease
Low TSH + High T4	Hyperthyroidism
High TSH + Low T4	Hypothyroidism
High lipase	Pancreatitis
Low albumin + edema	Nephrotic syndrome
High lactate	Shock

SECTION 111: COMPLEX MULTI-SYSTEM CASES

Case 1: Elderly Diabetic with Sepsis

Labs:

WBC: 22,000
Platelets: 85,000
Creatinine: 3.0
Lactate: 6 mmol/L
Bilirubin: 3.5
INR: 2.1

Interpretation:

Severe sepsis
Acute kidney injury
Early liver dysfunction
Coagulopathy

Diagnosis: Septic shock with multi-organ dysfunction.

Clinical pearl: Lactate >4 predicts poor prognosis.

Case 2: Cirrhosis with Confusion

Labs:

Bilirubin elevated
Albumin low
INR prolonged
Ammonia high

Diagnosis: Hepatic encephalopathy.

Key marker: Elevated ammonia.

Case 3: Severe Trauma Patient

Labs:

Hemoglobin falling
Platelets decreasing
PT prolonged
Fibrinogen low
D-dimer high

Diagnosis: Disseminated intravascular coagulation (DIC).

SECTION 112: RARE METABOLIC DISORDERS

1. Wilson Disease

Labs:

Low ceruloplasmin
High urinary copper
Elevated liver enzymes

Young patient with liver + neuro symptoms.

2. Hemochromatosis

Labs:

High ferritin
High transferrin saturation
Normal or high iron

Iron overload disorder.

3. G6PD Deficiency

Labs during hemolysis:

High LDH
High indirect bilirubin
Low haptoglobin

Triggered by infection or certain drugs.

SECTION 113: INBORN ERRORS OF METABOLISM

1. Phenylketonuria (PKU)

Elevated phenylalanine levels.

Newborn screening test critical.

2. Maple Syrup Urine Disease

Elevated branched-chain amino acids.

3. Urea Cycle Disorder

Labs:

High ammonia
Normal liver enzymes

Neonatal emergency.

SECTION 114: HEMATOLOGICAL MALIGNANCY PANELS

Acute Leukemia

Labs:

Very high or very low WBC
Blasts on peripheral smear
Low platelets
Low hemoglobin

Bone marrow confirmation required.

Chronic Myeloid Leukemia (CML)

Labs:

High WBC
Basophilia
Low LAP score
BCR-ABL positive

Lymphoma

Labs:

Elevated LDH
Anemia
Possible cytopenias

SECTION 115: ADVANCED ACID-BASE DISORDERS

Mixed Disorder Example

pH: 7.25
PaCO₂: 60
HCO₃⁻: 18

Interpretation:

Both respiratory acidosis and metabolic acidosis.

Mixed disorder.

Salicylate Poisoning

Early:

Respiratory alkalosis

Late:

Metabolic acidosis

Classic exam question.

SECTION 116: ENDOCRINE EMERGENCIES

1. Thyroid Storm

Labs:

Very low TSH
Very high T3/T4

Clinical emergency.

2. Myxedema Coma

Labs:

High TSH
Low T4
Hyponatremia
Hypoglycemia

3. Adrenal Crisis

Labs:

Low cortisol
Low sodium
High potassium
Low glucose

Life-threatening.

SECTION 117: ICU TOXIC-METABOLIC STATES

1. Lactic Acidosis

High lactate
Low pH
High anion gap

Seen in shock.

2. Ethylene Glycol Poisoning

High anion gap
High osmolar gap

3. Tumor Lysis Syndrome

High potassium
High uric acid
High phosphate
Low calcium

Oncology emergency.

SECTION 118: ADVANCED DIFFERENTIAL TABLE

Lab Pattern	Possible Diagnosis
Pancytopenia	Aplastic anemia
Hypercalcemia + Low PTH	Malignancy
Hyperkalemia + Acidosis	Renal failure
Low sodium + High urine osmolality	SIADH
High ferritin + Inflammation	Acute phase reaction

SECTION 119: POSTGRADUATE VIVA PEARLS

Always calculate anion gap in metabolic acidosis.
Check albumin when interpreting calcium.
Creatinine alone is insufficient; use eGFR.
Always correlate thyroid tests with clinical signs.
In suspected DIC, check fibrinogen.
Lactate trend is more important than single value.
Interpret ferritin carefully in inflammatory states.

SECTION 121: MOLECULAR DIAGNOSTICS

Modern medicine increasingly uses molecular-level testing.

1. PCR (Polymerase Chain Reaction)

Used to detect:

Viral infections (HIV, HBV, HCV)
Tuberculosis
COVID-like respiratory viruses
Genetic mutations

Key Concept: Detects genetic material — highly sensitive.

2. BCR-ABL Mutation

Seen in: Chronic Myeloid Leukemia (CML)

Used to:

Confirm diagnosis
Monitor treatment response

3. JAK2 Mutation

Seen in: Polycythemia vera
Essential thrombocythemia

4. BRCA1 / BRCA2

Associated with: Breast and ovarian cancers

Used in risk assessment.

SECTION 122: TRANSPLANT MEDICINE LAB MONITORING

1. Kidney Transplant

Monitor:

Creatinine
eGFR
Tacrolimus levels
Urinalysis

Rising creatinine → Possible rejection.

2. Liver Transplant

Monitor:

ALT
AST
Bilirubin
INR

Sudden elevation → Rejection or biliary complication.

3. Immunosuppressant Monitoring

Tacrolimus: 5–15 ng/mL therapeutic range

Cyclosporine: 100–400 ng/mL (varies by protocol)

SECTION 123: ADVANCED ONCOLOGY BIOMARKERS

1. HER2

Used in: Breast cancer

Guides targeted therapy.

2. PD-L1

Used in: Immunotherapy decisions

3. PSA Velocity

Rapid increase suggests aggressive prostate cancer.

4. Beta-hCG

Elevated in: Germ cell tumors
Choriocarcinoma

SECTION 124: IMMUNOLOGY LAB INTEGRATION

Complement Levels

C3 and C4 low in:

Active SLE
Immune complex diseases

Immunoglobulin Levels

IgG, IgA, IgM

Low levels: Immunodeficiency

High levels: Chronic infection, autoimmune disease

SECTION 125: CRITICAL CARE BIOCHEMISTRY

Lactate Clearance

Reduction over 6 hours indicates improvement in sepsis.

Mixed Venous Oxygen Saturation (SvO₂)

Normal: 60–80%

Low → Poor tissue oxygen delivery.

Procalcitonin Trends

Used to guide antibiotic discontinuation.

SECTION 126: ADVANCED ELECTROLYTE DISORDERS

Pseudohyponatremia

Occurs in:

Hyperlipidemia
Hyperproteinemia

Measured sodium low but serum osmolality normal.

Pseudohyperkalemia

Due to:

Hemolysis
Delayed sample processing

SECTION 127: LAB VALUES IN PREGNANCY – ADVANCED

Physiological changes:

Hemoglobin decreases
WBC mildly increases
Alkaline phosphatase increases
D-dimer elevated
Fibrinogen elevated

Important: Interpret cautiously to avoid overdiagnosis.

SECTION 128: LAB VALUES IN COVID-LIKE SEVERE VIRAL INFECTION

Common patterns:

Lymphopenia
Elevated CRP
Elevated D-dimer
Elevated ferritin
Elevated IL-6

Severe cases show cytokine storm pattern.

SECTION 129: LAB VALUES IN AUTOIMMUNE CYTOKINE STORM

Markers:

Ferritin very high
CRP elevated
IL-6 elevated
D-dimer elevated

Seen in:

Severe inflammatory syndromes
Macrophage activation syndrome

SECTION 130: RESEARCH-LEVEL BIOMARKERS

Troponin Ultra-Sensitive Assays

Detect myocardial injury earlier.

Galectin-3

Heart failure biomarker.

ST2

Cardiac remodeling marker.

SECTION 131: LAB STATISTICS FOR POSTGRADUATES

Understand:

Confidence intervals
Reference interval shifts
False positives
False negatives

Always ask:

Is this clinically significant?

SECTION 132: MASTER DIFFERENTIAL STRATEGY

When lab abnormal:

Confirm value
Repeat if necessary
Assess severity
Correlate clinically
Evaluate trend
Identify reversible causes
Act if life-threatening

SECTION 134: ULTRA-COMPLEX ICU CASES

Case 1: Septic Diabetic with Renal Failure

Labs:

Glucose: 420
pH: 7.21
HCO₃⁻: 14
Anion gap: 24
Creatinine: 3.2
Potassium: 5.8
Lactate: 5

Interpretation:

Diabetic ketoacidosis
Acute kidney injury
Lactic acidosis
Hyperkalemia

Mixed metabolic acidosis (DKA + lactic acidosis).

Case 2: Post-Surgery Deterioration

Labs:

Platelets: 70,000
PT prolonged
Fibrinogen low
D-dimer very high

Diagnosis: Disseminated intravascular coagulation (DIC).

Case 3: Cirrhotic Patient with Shock

Labs:

Bilirubin: 6
Albumin: 2.1
INR: 2.5
Creatinine rising
Lactate elevated

Diagnosis:

Acute-on-chronic liver failure with hepatorenal syndrome.

SECTION 135: ADVANCED ACID–BASE INTEGRATION

Case 4: Salicylate Toxicity

pH: 7.46
PaCO₂: 28
HCO₃⁻: 18

Interpretation:

Mixed respiratory alkalosis + metabolic acidosis.

Classic poisoning pattern.

Case 5: COPD with Vomiting

pH: 7.37
PaCO₂: 60
HCO₃⁻: 34

Interpretation:

Chronic respiratory acidosis + metabolic alkalosis.

Mixed disorder.

SECTION 136: HEMATOLOGY–ONCOLOGY DEPTH

Case 6: Pancytopenia

Hb low
WBC low
Platelets low

Possible causes:

Aplastic anemia
Leukemia
Bone marrow infiltration

Further test: Bone marrow biopsy.

Case 7: Tumor Lysis Syndrome

Potassium: 6.5
Phosphate high
Calcium low
Uric acid high

Oncology emergency.

SECTION 137: ENDOCRINE-METABOLIC CRISES

Case 8: Adrenal Crisis

Sodium: 120
Potassium: 6.2
Glucose: 50
Cortisol low

Life-threatening emergency.

Case 9: Thyroid Storm

TSH undetectable
T4 extremely high
Liver enzymes mildly elevated

Hypermetabolic crisis.

SECTION 138: TRANSPLANT REJECTION PATTERN

Kidney transplant patient:

Creatinine rising
Proteinuria
Tacrolimus level low

Likely acute rejection.

SECTION 139: POSTGRADUATE MCQs WITH EXPLANATIONS

MCQ 1

High ferritin with low transferrin saturation suggests?

Answer: Anemia of chronic disease.
Reason: Ferritin is acute-phase reactant.

MCQ 2

Hyperkalemia ECG change first?

Answer: Peaked T waves.

MCQ 3

Low calcium with high phosphate suggests?

Answer: Hypoparathyroidism.

MCQ 4

High anion gap acidosis causes?

Answer: DKA, lactic acidosis, toxins.

MCQ 5

Troponin elevated without chest pain?

Possible causes:

Renal failure
Myocarditis
Sepsis

MCQ 6

Low sodium with high urine osmolality?

Answer: SIADH.

MCQ 7

Albumin low in which condition?

Chronic liver disease
Nephrotic syndrome

MCQ 8

Which lab rises first in MI?

Troponin (high-sensitivity assays).

MCQ 9

Elevated ALP in child?

Normal due to bone growth.

MCQ 10

Corrected calcium formula used when?

Albumin low.

(Continuing rapid-fire high-yield style)

MCQ 11

Low TSH, normal T4?

Subclinical hyperthyroidism.

MCQ 12

High ESR but normal CRP?

Chronic inflammation.

MCQ 13

Creatinine normal but GFR reduced?

Possible early CKD.

MCQ 14

High ammonia with normal LFT?

Urea cycle disorder.

MCQ 15

Sepsis marker most specific?

Procalcitonin.

(Additional condensed rapid review)

MCQ 16

High calcium + low PTH → Malignancy.

MCQ 17

High PTH + low calcium → Secondary hyperparathyroidism.

MCQ 18

AST>ALT (>2) → Alcoholic hepatitis.

MCQ 19

High CK-MB but normal troponin → Possible muscle injury.

MCQ 20

Severe hyponatremia correction rate?
8–10 mEq/L per 24 hours.

SECTION 140: CONSULTANT-LEVEL PRINCIPLES

Always suspect mixed disorders in ICU.
Recalculate anion gap manually.
Check albumin in calcium abnormalities.
Interpret ferritin cautiously in infection.
Evaluate trends over 24–72 hours.
Confirm critical values immediately.
Think pathophysiology, not just numbers.

MASTER CLOSING STATEMENT (SO FAR)

At this stage, this article now covers:

Foundational values
Advanced panels
Clinical algorithms
ICU reasoning
Rare disorders
Molecular diagnostics
Transplant monitoring
Mixed acid–base disorders
40+ clinical cases
Advanced MCQs

NORMAL LABORATORY VALUES A Complete Clinical and Diagnostic Guide

NORMAL LABORATORY VALUES

Introduction

SECTION 1: HEMATOLOGY

1. Complete Blood Count (CBC)

1. Hemoglobin (Hb)

Clinical Significance

2. Red Blood Cell Count (RBC)

3. Hematocrit (HCT / PCV)

4. White Blood Cell Count (WBC)

5. Differential Leukocyte Count (DLC)

Clinical Interpretation

6. Platelet Count

SECTION 2: RED CELL INDICES

1. Mean Corpuscular Volume (MCV)

2. Mean Corpuscular Hemoglobin (MCH)

3. Mean Corpuscular Hemoglobin Concentration (MCHC)

SECTION 3: RENAL FUNCTION TESTS (RFTs)

1. Serum Creatinine

2. Blood Urea Nitrogen (BUN)

3. Estimated GFR (eGFR)

SECTION 4: ELECTROLYTES

1. Sodium (Na⁺)

2. Potassium (K⁺)

3. Chloride (Cl⁻)

4. Bicarbonate (HCO₃⁻)

SECTION 5: LIVER FUNCTION TESTS (LFTs)

1. ALT (SGPT)

2. AST (SGOT)

3. Alkaline Phosphatase (ALP)

4. Total Bilirubin

SECTION 6: BLOOD GLUCOSE VALUES

HbA1c

SECTION 7: LIPID PROFILE

SECTION 8: COAGULATION PROFILE

1. Prothrombin Time (PT)

2. International Normalized Ratio (INR)

3. Activated Partial Thromboplastin Time (aPTT)

4. Bleeding Time

SECTION 9: THYROID FUNCTION TESTS (TFTs)

1. Thyroid Stimulating Hormone (TSH)

2. Free T4

3. Free T3

Interpretation Pattern

SECTION 10: CARDIAC MARKERS

1. Troponin I / T

2. CK-MB

3. BNP (Brain Natriuretic Peptide)

SECTION 11: PANCREATIC ENZYMES

1. Serum Amylase

2. Serum Lipase

SECTION 12: ARTERIAL BLOOD GAS (ABG)

Normal ABG Values

Acid-Base Disorders

SECTION 13: URINALYSIS

1. Physical Examination

2. Chemical Examination

3. Microscopy

SECTION 14: INFLAMMATORY MARKERS

1. ESR (Erythrocyte Sedimentation Rate)

2. C-Reactive Protein (CRP)

SECTION 15: SERUM PROTEINS

1. Total Protein

2. Albumin

3. Globulin

SECTION 16: CALCIUM & BONE PROFILE

1. Serum Calcium

2. Serum Phosphate

3. Vitamin D (25-OH)

SECTION 17: MAGNESIUM

SECTION 18: TUMOR MARKERS

1. Alpha-Fetoprotein (AFP)

2. Carcinoembryonic Antigen (CEA)

3. Prostate-Specific Antigen (PSA)

4. CA-125

5. CA 19-9

SECTION 19: HORMONAL ASSAYS

1. Serum Cortisol

2. Prolactin

3. LH (Luteinizing Hormone)