Blood Test Guide
Understanding Your Blood Test Results
8 min read · Educational guide
Reference ranges can vary between laboratories. Always use the ranges printed on your specific lab report, and consult your doctor for interpretation.
How to Read a Blood Test Report
A blood test report lists each test, your result value, the reference range (normal range), and a flag (H = high, L = low, * = critical). Focus first on any flagged values, then discuss with your doctor. A single abnormal value rarely tells the full story — context and trends matter more.
Complete Blood Count (CBC)
Hemoglobin (Hb)
Normal: M: 13–17 g/dL · F: 12–15 g/dLIf LOW
Anaemia — fatigue, weakness, breathlessness. Most common cause: iron deficiency.
If HIGH
Polycythaemia — thickened blood. Can increase clot risk.
WBC / TLC
Normal: 4,000–11,000 cells/μLIf LOW
Leukopenia — weakened immunity. Check for viral infections, bone marrow issues.
If HIGH
Leukocytosis — active infection, inflammation, or leukaemia in extreme cases.
Platelets / TPC
Normal: 1.5–4.0 lakh/μL (150,000–400,000)If LOW
Thrombocytopenia — bleeding risk. Dengue commonly causes sudden platelet drop.
If HIGH
Thrombocytosis — clotting risk. May be reactive (after infection) or primary.
MCV
Normal: 80–100 fLIf LOW
Small red blood cells — iron deficiency or thalassemia.
If HIGH
Large red blood cells — B12 or folate deficiency.
Blood Sugar
Fasting Blood Sugar (FBS)
Normal: 70–100 mg/dLIf LOW
Hypoglycaemia — dizziness, sweating, confusion. Needs immediate glucose.
If HIGH
100–125 = pre-diabetes. ≥126 mg/dL on two tests = diabetes.
HbA1c (Glycated Haemoglobin)
Normal: <5.7%If LOW
N/A (low HbA1c is not a concern unless hypoglycaemia symptoms present)
If HIGH
5.7–6.4% = pre-diabetes. ≥6.5% = diabetes. Shows 3-month average sugar control.
Post-Prandial Sugar (PPBS)
Normal: <140 mg/dL (2h after meal)If LOW
Not clinically significant
If HIGH
140–199 = impaired glucose tolerance. ≥200 = likely diabetes.
Lipid Profile (Cholesterol)
Total Cholesterol
Normal: <200 mg/dLIf LOW
Not usually a concern
If HIGH
200–239 = borderline high. ≥240 = high risk for heart disease.
LDL ("Bad" Cholesterol)
Normal: <100 mg/dL (ideal)If LOW
Better for heart health
If HIGH
>130 mg/dL = elevated risk. >160 = high. Consider lifestyle changes or statins.
HDL ("Good" Cholesterol)
Normal: M: >40 · F: >50 mg/dLIf LOW
Low HDL = higher heart disease risk. Increase with exercise and healthy fats.
If HIGH
High HDL is protective.
Triglycerides
Normal: <150 mg/dLIf LOW
Not a concern
If HIGH
150–199 = borderline. ≥500 = risk of pancreatitis. Linked to high-carb diets, alcohol.
Kidney Function Test (KFT / RFT)
Serum Creatinine
Normal: M: 0.7–1.3 · F: 0.6–1.1 mg/dLIf LOW
Not significant
If HIGH
Indicates reduced kidney filtering ability. Trend over time matters more than single value.
Blood Urea Nitrogen (BUN)
Normal: 7–20 mg/dLIf LOW
May indicate low protein intake or liver disease
If HIGH
Elevated in kidney disease, dehydration, or high protein diet.
eGFR
Normal: >60 mL/min/1.73m²If LOW
<60 for 3+ months = chronic kidney disease. <15 = kidney failure.
If HIGH
Higher is better for kidney function.
Uric Acid
Normal: M: 3.5–7.2 · F: 2.6–6.0 mg/dLIf LOW
Not clinically significant
If HIGH
>7.2 in men = hyperuricemia — risk of gout. Reduce red meat, alcohol.
Liver Function Test (LFT)
SGOT / AST
Normal: 10–40 U/LIf LOW
Not significant
If HIGH
Liver damage, heart muscle injury. >3x normal with symptoms needs urgent evaluation.
SGPT / ALT
Normal: 7–56 U/LIf LOW
Not significant
If HIGH
More specific for liver damage than SGOT. Elevated in hepatitis, fatty liver, alcohol.
Total Bilirubin
Normal: 0.2–1.2 mg/dLIf LOW
Not significant
If HIGH
>1.2 = jaundice risk. Can be pre-hepatic (haemolysis), hepatic (liver disease), or post-hepatic (bile duct blockage).
Serum Albumin
Normal: 3.5–5.0 g/dLIf LOW
Indicates chronic liver disease, malnutrition, or protein-losing conditions.
If HIGH
Not typically a concern
Thyroid (TSH / T3 / T4)
TSH (Thyroid Stimulating Hormone)
Normal: 0.4–4.0 mIU/LIf LOW
<0.4 = hyperthyroidism — weight loss, palpitations, sweating, anxiety.
If HIGH
>4.0 = hypothyroidism — weight gain, fatigue, cold intolerance, hair loss.
Free T4 (FT4)
Normal: 0.8–1.8 ng/dLIf LOW
Hypothyroidism (confirmed with high TSH)
If HIGH
Hyperthyroidism (confirmed with low TSH)
Free T3 (FT3)
Normal: 2.3–4.1 pg/mLIf LOW
Hypothyroidism or non-thyroidal illness
If HIGH
Hyperthyroidism, especially T3 toxicosis
Critical Values — Seek Immediate Care
⚠ Haemoglobin < 7 g/dL
⚠ Platelets < 50,000/μL
⚠ Potassium (K+) < 2.5 or > 6.5 mEq/L
⚠ Sodium (Na+) < 120 or > 160 mEq/L
⚠ Blood Sugar < 50 or > 500 mg/dL
⚠ Creatinine > 10 mg/dL
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