Blood Tests A–Z: Normal Ranges Explained

Quick answer

This A–Z guide explains common blood tests in plain language: what each test measures, its normal range, and what high or low results mean, from CBC and cholesterol to thyroid, liver, kidney, iron and vitamin tests. Use the table below to find your test, then click through for a full page on each result.

How reference ranges work

Every blood test result is accompanied by a reference range, the interval within which most healthy people fall. These ranges are not arbitrary: they are typically derived from the central 95% of measurements in a healthy reference population, defined using statistical methods recommended by international clinical laboratory bodies.¹ The practical consequence is that 1 in 20 completely healthy people will have at least one result outside the reference range purely by chance. A single mildly abnormal value in an otherwise well person is therefore not automatically cause for concern, context matters as much as the number.

Several factors shift results without implying disease. Age-specific and sex-specific ranges exist for many tests (haemoglobin, creatinine, and several hormones differ between men and women and change across the lifespan). Pregnancy changes reference intervals substantially. Timing matters for hormone tests such as cortisol and testosterone, which peak in the morning. Fasting is required for glucose and lipid profiles. The laboratory performing the test should print its own reference range on the result, since equipment, reagents and local population characteristics can produce slightly different thresholds between institutions. When a result is unexpected, a repeat test after confirming correct preparation is usually the appropriate first step.

The A-to-Z table below lists typical adult ranges and what each test is used for. Use it as a starting point, not a substitute for advice from the clinician who ordered the test.

A

Test	Normal Range	What it measures
Albumin	3.5–5.0 g/dL	Main blood protein; low in liver disease, malnutrition, kidney disease
ALP (Alkaline Phosphatase)	44–147 U/L	Liver/bile duct or bone disease
ALT (Alanine aminotransferase)	7–56 U/L	Liver cell damage: most specific liver enzyme
ANA	Negative / <1:40	Autoimmune screening: lupus, Sjögren's, scleroderma
AST (Aspartate aminotransferase)	10–40 U/L	Liver and muscle damage

Key points

Reference ranges come from the middle 95 percent of healthy people and vary by lab, age, sex and pregnancy.
Use the tables to find your test, then read the linked full page for detail.
A flagged result needs context: size of deviation, symptoms and other results.
Ranges are a guide, not a verdict.

B

Test	Normal Range	What it measures
Bilirubin (total)	0.1–1.2 mg/dL	Jaundice: liver, bile duct or haemolysis
BNP / NT-proBNP	BNP <100 pg/mL	Heart failure: stretching of heart chambers
Blood urea / BUN	7–20 mg/dL	Kidney function and hydration status

C

Test	Normal Range	What it measures
Calcium	8.5–10.5 mg/dL	Bone health, parathyroid, kidney, malignancy
CBC / FBC	See individual parameters	Red cells, white cells, platelets: full picture
Cholesterol (LDL)	<100 mg/dL optimal	Heart disease risk: main statin target
CK (Creatine Kinase)	55–170 U/L	Muscle damage: myopathy, rhabdomyolysis
Creatinine	Men: 0.74–1.35 mg/dL; Women: 0.59–1.04 mg/dL	Kidney waste product: rises as kidneys fail
CRP	<10 mg/L	Inflammation: rises quickly with infection or flare

D, G

Test	Normal Range	What it measures
D-Dimer	<0.5 mg/L	Blood clot activity: DVT, PE screening
ESR	Men: <15 mm/hr; Women: <20 mm/hr	Chronic inflammation: slower than CRP
Ferritin	Men: 24–336 ng/mL; Women: 11–307 ng/mL	Iron stores: most sensitive iron deficiency marker
GGT (Gamma-GT)	Men: <71 U/L; Women: <42 U/L	Liver/bile duct + alcohol marker
Glucose (fasting)	70–100 mg/dL	Diabetes screening and monitoring

H, M

Test	Normal Range	What it measures
HbA1c	<5.7% normal; 5.7–6.4% pre-diabetes; ≥6.5% diabetes	Average blood sugar over 3 months
Haemoglobin	Men: 13.5–17.5; Women: 12.0–15.5 g/dL	Oxygen carrier: low = anaemia
HDL Cholesterol	Men: >40 mg/dL; Women: >50 mg/dL	"Good" cholesterol: protective against heart disease
INR	0.8–1.2 (2.0–3.0 on warfarin)	Blood clotting time: liver function and warfarin monitoring
LDH	140–280 U/L	Cell damage: haemolysis, heart attack, cancer
LFT panel	See individual tests	Liver health: enzymes + synthetic function
Magnesium	1.7–2.2 mg/dL	Electrolyte: arrhythmia risk when low

P, Z

Test	Normal Range	What it measures
Phosphorus	2.5–4.5 mg/dL	Bone mineral: rises in kidney disease
Platelets	150,000–400,000/µL	Clotting cells: low = bleeding risk; high = clot risk
Potassium	3.5–5.0 mEq/L	Electrolyte: heart rhythm critical; high dangerous
PSA	<4.0 ng/mL	Prostate cancer screening in men
Sodium	136–145 mEq/L	Fluid balance: hyponatraemia common in elderly
Testosterone (total, men)	300–1,000 ng/dL	Male hormone: low causes fatigue, reduced libido
Troponin	<0.04 ng/mL (varies by lab)	Heart muscle damage: definitive heart attack test
TSH	0.4–4.0 mIU/L	Thyroid function: low in hyperthyroid; high in hypothyroid
Uric Acid	Men: 3.5–7.2 mg/dL; Women: 2.6–6.0 mg/dL	Gout: crystals in joints when high
Vitamin B12	200–900 pg/mL	Nerve and red cell health
Vitamin D (25-OH)	30–100 ng/mL	Bone and immune health
WBC (white count)	4,500–11,000/µL	Immune cells: high = infection; low = marrow/viral
Zinc	70–120 mcg/dL	Immune function, wound healing, taste

Not every test on this list is a simple "high means disease" story. PSA is a good example: in a large US screening trial, testing men aged 55–69 prevented roughly 1.3 prostate cancer deaths per 1,000 men screened over 13 years, but at the cost of frequent false-positive results, unnecessary biopsies, and overtreatment, about 1 in 5 men who have surgery for a screen-detected cancer develop long-term urinary incontinence and 2 in 3 experience long-term erectile dysfunction. This is why current US guidance treats PSA screening as an individual decision made with a clinician rather than a routine test for every man.³

Your next steps when you get a blood report

Read the range printed on your own report
Reference ranges differ between laboratories and analysers — the interval next to your value is the one that counts, not a range found online.
Note the flagged lines
H (high) or L (low) flags mark values outside the range. One flagged line is a starting point, not a diagnosis.
Look the test up in the A–Z tables above
Use the tables to understand what each flagged test measures, then read the linked full page for detail.
Think in trends, not snapshots
A single borderline value matters less than the direction over time — compare with previous reports from the same lab where possible.
Prepare questions for your doctor
Ask what the flagged value could mean in your context, whether it needs repeating, and what would change the interpretation.
Don’t self-diagnose from one flag
Deviation size, symptoms and the other results together are what give a number meaning.

The most-ordered tests at a glance

The tests doctors order most often, with what a flagged result usually prompts them to consider — context, not conclusions:

Test	High value often prompts a check of	Low value often prompts a check of
CBC (haemoglobin, WBC, platelets)	Infection, inflammation, dehydration, marrow disorders	Anaemia, bleeding, marrow suppression, viral illness
Fasting glucose / HbA1c	Diabetes, pre-diabetes	Hypoglycaemia causes, over-treatment in diabetics
Lipid profile	Cardiovascular risk, diet, thyroid	Malnutrition, hyperthyroidism, liver disease
Creatinine / eGFR	Kidney function, dehydration, medication effects	Low muscle mass, pregnancy (interpret with care)
ALT / AST	Liver injury, alcohol, fatty liver, medicines	Rarely clinically significant on its own
TSH	Hypothyroidism	Hyperthyroidism, over-replacement
Vitamin D	Over-supplementation	Deficiency: bone health, sunlight, diet
CRP / ESR	Infection, inflammation, flare of chronic disease	Not usually clinically meaningful

Each of these has a full page on this site — search the test name for the detailed guide.

Practical notes

There is no universal preparation rule: fasting depends entirely on which tests were ordered. Always check with the ordering doctor or the lab — guessing wrong means a wasted visit and a repeat draw.

Ask what each ordered test is looking for, and bring previous reports so new results can be read as trends. A report makes far more sense when you know the question it was ordered to answer.

Read every result against the reference range printed on your own report — ranges differ between laboratories, methods, age and sex, and a value flagged at one lab can be normal at another. A single flagged value is a prompt for interpretation, not a diagnosis.

Borderline or unexpected results usually mean ‘discuss and possibly repeat’, not panic. When your doctor advises a repeat, using the same laboratory keeps the numbers comparable across visits.

In India

In India, common individual tests typically cost a few hundred rupees each and panels cost more, though prices vary by city and lab. If several tests are ordered together, ask about a bundled price before paying per test.

Choose an NABL-accredited laboratory, with home sample collection available in most major cities. The reference range printed on your own report is the one that counts — it reflects that lab’s own methods.

Frequently Asked Questions

What is a reference range on a blood test?

A reference range is the interval of values found in 95% of healthy adults. Results outside the range are flagged as high (H) or low (L). Reference ranges differ between laboratories depending on the analyser and method used, so always compare your result to the range printed on your own laboratory report rather than values found online.

How do I read my blood test results?

Each line of a blood test result shows: the test name and abbreviation, your measured value, the unit (e.g. mmol/L, g/dL), and the laboratory's reference range. A flag of H or L beside the result means your value falls outside the reference range. One abnormal result rarely means disease, context, symptoms, and trends over time are what matter.

What are the most commonly ordered blood tests?

The most frequently ordered tests are: CBC (complete blood count) for red cells, white cells and platelets; metabolic panels for kidney and electrolytes; liver function tests (LFTs) for liver health; lipid profile for cardiovascular risk; HbA1c and fasting glucose for diabetes; thyroid function (TSH, T4) for thyroid disorders; and vitamin D and B12 for nutritional status.

Why might a blood test result be falsely abnormal?

Common causes of falsely abnormal results include: not fasting when required (affects glucose, triglycerides), haemolysis during sample collection (artificially raises potassium), dehydration (concentrates all values), medications (steroids raise glucose, diuretics lower potassium), time of day (cortisol peaks in the morning), and laboratory error. Always discuss unexpected results with your doctor before acting on them.

My report flags a value in red — does that mean I’m ill?

Not necessarily. A flag only means the value sits outside that lab’s reference range — many flagged values are mild, transient, or explained by timing, food or exercise. Discuss it with your doctor before worrying.

Can I compare my results with my friend’s report?

Only very loosely. Different laboratories use different methods and reference ranges, so the same number can be normal on one report and flagged on another. Compare each result with its own report’s range instead.

Why is the reference range different on my new report?

Reference ranges depend on the laboratory’s equipment and method, which is exactly why the range printed on your own report is the one that counts. A changed range usually reflects a changed method, not a changed you.

How long should I keep my old blood reports?

Keep them indefinitely — digital copies are fine. Trends across months and years help your doctor interpret new results far better than any single report can.

References

The clinical information on this page is drawn from peer-reviewed sources indexed by the US National Library of Medicine. Links go to the source so you can read it yourself.

Ozarda Y. Reference intervals: current status, recent developments and future considerations. Biochem Med (Zagreb). 2016;26(1):5–16. PMID 26981015 · doi:10.11613/BM.2016.001
Lee TS, Kim J, Uh Y, Park YC, Yoo GS, Yoon KJ. Correction Equation for Estimation of Actual Potassium Concentration in Hemolyzed Specimen. Clin Lab. 2017;63(2):271–275. PMID 28182346 · doi:10.7754/Clin.Lab.2016.160733
US Preventive Services Task Force. Screening for Prostate Cancer: US Preventive Services Task Force Recommendation Statement. JAMA. 2018;319(18):1901–1913. PMID 29801017 · doi:10.1001/jama.2018.3710

Medical Disclaimer: For educational purposes only. Always consult a qualified healthcare professional for diagnosis and treatment.