Blood Test Guide- Reference Range and Their Interpretation

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Common Blood Tests: A Quick Reference Guide for Adults

Category	Test Marker	Adult Reference Range	Why doctors order this test
CBC	Hemoglobin	13.5–17.5 g/dL (male), 12.0–15.5 g/dL (female). Different labs use slightly different limits.	Detect anemia or excess red blood cells
	WBC Count	4,000–11,000/µL. Some labs use 10,000 as the upper limit.	Look for infection, inflammation or blood disorders
	Platelet Count	1,50,000 – 4,00,000 /mcL. The upper limit is not standard. If lower than 1,50,000, doctors check the numbers against other tests and symptoms to determine the reason.	Assess blood clotting and bleeding risk
Diabetes	Fasting Sugar	70–99 mg/dL (Normal), 100–125 (Prediabetes), ≥126 suggests diabetes if confirmed on repeat testing. Overnight fast (8–12 hours) is essential.	Screen for diabetes and prediabetes
	HbA1c	<5.7% Normal, 5.7–6.4% Prediabetes, ≥6.5% suggests diabetes (usually confirmed with repeat testing or other diagnostic criteria).	Assess average blood sugar over the last 2–3 months
Kidney & Electrolytes	Serum Creatinine	0.7 – 1.3 mg/dL. Can rise temporarily with dehydration, intense exercise and large meat meals.	Assess kidney function, in conjunction with other tests.
	eGFR	≥90 mL/min/1.73 m². Lower values may be OK with age. Usually more informative than creatinine alone.	Estimate how well the kidneys filter blood
	Sodium	135-145 meq/L. Sodium and Potassium in the blood need a fine balance.	Evaluate body fluid and electrolyte balance
	Potassium	3.5–5.1 mEq/L	Check nerve, muscle and heart function
	Uric Acid	3.4 – 7.2 mg/dL (male), 2.4-6 (female). Some labs have slightly different norms.	Help evaluate gout and uric acid kidney stone risk.
Lipids	Total Cholesterol	Desirable: <200 mg/dL. Levels upto 239 are considered borderline high, while levels over 240 are considered high.	Part of cardiovascular risk assessment.
	LDL Cholesterol	< 100 mg/dL. Need to be managed to lower levels in case of known cardiovascular risks.	Estimate risk of heart attack and stroke
	HDL Cholesterol	>40 mg/dL (men), >50 mg/dL (women).  ≥60 mg/dL is considered protective.	Assess protective cholesterol level
	Total Triglycerides	<150 mg/dL. Levels upto 199 are considered borderline, upto 499 as high, and beyond that very high. The numbers can be influenced by food.	Assess metabolic and cardiovascular risk
Thyroid-related	TSH	0.4 – 4.0 mIU/L. Higher levels usually  indicate hypothyroidism. To be read with other thyroid tests.	Screen for thyroid disorders
Liver-related	ALT (SGPT)	7–56 U/L. Higher levels may indicate liver injury.	Detect liver cell injury
	AST (SGOT)	10–40 U/L	Evaluate liver or muscle injury
	Total Bilirubin	0.3–1.2 mg/dL. Higher levels may indicate jaundice.	Assess jaundice and liver or bile duct disorders
	Albumin	3.5–5.0 g/dL	Evaluate liver function, nutrition and kidney disorders
Others	Vitamin D3	30–50 ng/mL is generally considered sufficient. Many authorities accept 20–50 in healthy adults.	Assess vitamin D status and bone health.
	Vitamin B12	220-900 pg/mL. Some labs use 200 instead of 220.	Detect deficiency causing anemia or nerve problems
	Ferritin	~30–300 ng/mL (men),  ~15–150 ng/mL (women). Low levels strongly suggest iron deficiency.	Assess iron stores in the body, and iron deficiency
	Serum Iron	~65–175 (men), ~50–170 µg/dL (women). Serum iron varies a lot during the day. Ferritin is a better indicator of iron in the body.	Help evaluate iron deficiency or iron overload
	CRP	<5 mg/L. Varies between labs.	Assess inflammation [does not identify the cause].

* Reference ranges vary slightly between labs. Always check the units (mg/dL, mmol/L, pg/mL, etc.) 

* Children, pregnant women and some medical conditions may have different reference ranges. For educational purposes only. 

* The readings should always be interpreted by a doctor in the context of symptoms and medical history.