Blood test normal range — what the numbers mean, and why your lab's differ

The two kinds of number

A diagnostic threshold is a cutoff published by a named body to define a condition. An HbA1c of 6.5% or above means diabetes because the American Diabetes Association defines it that way — on any analyser, in any country, in Bengaluru exactly as in Boston. These numbers are quotable, they change only when the body that issues them revises them, and they are the same for everyone.

A reference interval is the band one particular laboratory considers usual, measured on its own equipment against its own population. It is the range printed in the column next to your result. It is not wrong when it differs from another lab's — it is supposed to. TSH is the clearest case: the molecule is not fully standardised across manufacturers, so two analysers can return meaningfully different numbers from the same tube of blood, and each lab has to establish its own interval.

The practical rule: compare your result to the range on your own report, and use the published thresholds below to understand what the categories mean. A value flagged high against one lab's interval is a reason to ask a question, not a diagnosis.

Published thresholds, with sources

Each of these comes from the body named beneath it. Where the body has revised the number recently, that is said — because your report may still be printed against the older one.

Fasting plasma glucose

Category	Value
Normal	below 100 mg/dL
Prediabetes Called impaired fasting glucose	100 – 125 mg/dL
Diabetes	126 mg/dL or above

A diagnosis is not made on one reading. Without unmistakable symptoms, the ADA requires a second confirming test before diabetes is diagnosed.

Source: American Diabetes Association, Standards of Care in Diabetes — 2026, Section 2 · More on the Blood Glucose test

Two-hour glucose (75 g oral glucose tolerance test)

Category	Value
Normal	below 140 mg/dL
Prediabetes Called impaired glucose tolerance	140 – 199 mg/dL
Diabetes	200 mg/dL or above

A random glucose of 200 mg/dL or above, in someone with classic symptoms of high blood sugar, is diagnostic on its own.

Source: American Diabetes Association, Standards of Care in Diabetes — 2026, Section 2 · More on the Blood Glucose test

HbA1c

Category	Value
Normal	below 5.7%
Prediabetes	5.7% – 6.4%
Diabetes	6.5% or above

The ADA requires the test be run by an NGSP-certified method. HbA1c reflects roughly the previous three months, so it is unreliable in anyone whose red cells turn over unusually fast or slow — including in several forms of anaemia and haemoglobin variants, which are not rare in India.

Source: American Diabetes Association, Standards of Care in Diabetes — 2026, Section 2 · More on the HbA1c test

Haemoglobin below which anaemia is defined

Category	Value
Children 6–23 months	below 10.5 g/dL (105 g/L)
Children 24–59 months	below 11.0 g/dL (110 g/L)
Children 5–11 years	below 11.5 g/dL (115 g/L)
Children 12–14 years	below 12.0 g/dL (120 g/L)
Women 15+, not pregnant	below 12.0 g/dL (120 g/L)
Men 15+	below 13.0 g/dL (130 g/L)
Pregnancy, 1st trimester	below 11.0 g/dL (110 g/L)
Pregnancy, 2nd trimester	below 10.5 g/dL (105 g/L)
Pregnancy, 3rd trimester	below 11.0 g/dL (110 g/L)

These are the 2024 revision, which lowered two of the older cutoffs — infants 6–23 months and the second trimester of pregnancy both moved from 11.0 to 10.5 g/dL. A report printed against the older figures may call a child anaemic who is not, by the current definition. WHO also directs that the measured value be adjusted for altitude and for smoking before it is compared to these cutoffs.

Source: World Health Organization, Guideline on haemoglobin cutoffs to define anaemia in individuals and populations (2024) · More on the Haemoglobin test

eGFR — the kidney-function number calculated from creatinine

Category	Value
G1 — normal or high	90 or above
G2 — mildly reduced	60 – 89
G3a — mild to moderate	45 – 59
G3b — moderate to severe	30 – 44
G4 — severely reduced	15 – 29
G5 — kidney failure	below 15

All values in mL/min/1.73 m². These are stages, not a diagnosis: chronic kidney disease requires the reduction to have lasted at least three months, and KDIGO stages kidneys on eGFR together with albumin in the urine, not eGFR alone. Creatinine itself has no single normal value — it rises with muscle mass, which is why the same creatinine means different things in a large young man and a small elderly woman, and why the eGFR calculation exists.

Source: KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease · More on the Creatinine test

Triglycerides

Category	Value
Normal	below 150 mg/dL
Raised — fasting sample	150 mg/dL or above
Raised — non-fasting sample	175 mg/dL or above

The Lipid Association of India treats a raised triglyceride level as a risk modifier rather than a diagnosis on its own — it changes how the rest of the lipid profile is read, and the fasting and non-fasting cutoffs differ because triglycerides move more after a meal than cholesterol does.

Source: Lipid Association of India, Consensus Statement IV (2023 update on cardiovascular risk assessment and lipid management in Indian patients) · More on the Triglycerides test

hs-CRP, as a cardiovascular risk marker

Category	Value
Low vascular risk	below 1.0 mg/L
Moderate vascular risk	1.0 – 3.0 mg/L
High vascular risk	above 3.0 mg/L

These bands apply to the high-sensitivity test (hs-CRP) used for cardiovascular risk, and only in someone who is otherwise well. They say nothing useful during an infection or a flare of any inflammatory condition, when CRP rises far above this scale for reasons that have nothing to do with the heart — a standard CRP ordered to investigate an illness is a different question being asked of the same protein, and is not read against this table.

Source: CDC and American Heart Association, clinical guidelines on hs-CRP in global cardiovascular risk prediction (2003) · More on the CRP test

Where there is no universal number

For these, quoting a single national “normal” would be the mistake. What follows is why, and what to read instead.

LDL, HDL and total cholesterol

There is no single LDL number that is normal for everyone, and this is the one place where copying a generic chart does real harm. The Lipid Association of India sets the LDL target by the person's own cardiovascular risk — someone who has already had a heart attack is given a far lower target than someone with no risk factors at all, and the same LDL value can be fine for one and dangerous for the other. The Association also treats non-HDL cholesterol as a co-primary target alongside LDL, on the evidence that it predicts risk better in Indians. Which target applies to you is a calculation your doctor does from your risk factors, not a row in a table.

Source: Lipid Association of India, Consensus Statement IV (2023) · More on the Cholesterol test

Vitamin D — the thresholds were withdrawn

Laboratory	Value
Deficiency (2011 guidance)	below 20 ng/mL
Insufficiency (2011 guidance)	21 – 29 ng/mL
Sufficiency (2011 guidance)	30 – 100 ng/mL

These are shown because they are almost certainly the numbers printed on your report — and because they no longer carry the endorsement people assume. In 2024 the Endocrine Society stopped endorsing 30 ng/mL as a target and stopped endorsing the levels that define deficiency, insufficiency and sufficiency at all, judging that the trial evidence does not support thresholds that predict who benefits from supplementation. The same guideline advises against routine vitamin D testing in healthy adults. Most laboratory software still prints the old bands. A result flagged 'insufficient' against a threshold its own issuing body has stepped back from is worth discussing rather than acting on alone.

Source: Endocrine Society — 2011 Clinical Practice Guideline, and its 2024 successor

Why there is no universal normal for SGPT

Enzyme results are measurements of activity, not concentration, and that activity depends on the method and the temperature the assay runs at. Two labs using different methods can return genuinely different numbers from the same sample, which is why the upper limit printed beside your result varies from lab to lab and why no single national figure exists to quote. The same applies to SGOT, alkaline phosphatase and GGT. Read the value against the range in the column next to it, and the pattern across the panel rather than any one enzyme.

Source: Reference intervals are established by each laboratory; see CMAJ, 'What happens when laboratory reference ranges change?' (2020) · More on the SGPT (ALT) test

TSH — why your lab's range is the one that counts

Laboratory	Value
Quest Diagnostics, age 20+	0.40 – 4.50 mIU/L
Labcorp, age above 10	0.450 – 4.500 µIU/mL

Two large laboratories, two different intervals — and that is the point. TSH is not fully standardised across manufacturers: antibodies in different assays bind different parts of the molecule, so two analysers can return meaningfully different numbers from the same tube of blood. TSH also swings through the day, shifts with age, and moves with iodine intake, smoking and several medicines. The interval printed beside your result, by the lab that ran it, is the one to read it against — not a number from a website, including this one. In pregnancy the intervals change again by trimester.

Source: Published reference intervals of the named laboratories; assay variation per CMAJ, 'What happens when laboratory reference ranges change?' (2020) · More on the TSH test

Three things that trip people up

Your report may be printed against a withdrawn number. Laboratory software is updated slowly. The vitamin D bands above are the clearest example — most Indian reports still flag results against thresholds the Endocrine Society stopped endorsing in 2024 — but the WHO's 2024 revision of the anaemia cutoffs has the same problem in the other direction, and a child aged 6 to 23 months can be called anaemic by an older chart and not by the current one.

The unit changes the number, not the result. Indian labs mostly report in mg/dL; European and some international labs report the same measurement in mmol/L. A glucose of 100 mg/dL and one of 5.6 mmol/L are the same value. Converting before comparing matters most when you are reading an old report from a different lab, or one from abroad.

One value out of range is usually not the story. Reference intervals are commonly set to cover the middle 95% of a healthy population, which means one healthy person in twenty falls outside on any given test by definition. What a doctor reads is the pattern across the panel and the direction of travel across reports — which is the argument for keeping them all in one place.

The tests covered here

Each has its own page with the units it is reported in, how to convert between them, and what it measures.