Lancet Study: Why HbA1c Test is Unreliable for Diabetes Diagnosis in India

The Wake-Up Call from Lancet Everyone with High Sugar (or Family History) Needs to Read

I've seen it too many times — someone gets their HbA1c report, sees 6.7%, and suddenly they're "prediabetic." They panic, cut rice completely, start walking furiously, only to later discover their fasting sugar was fine and the test was thrown off by low iron. This isn't rare in India. A powerful new viewpoint from top experts, including Prof. Anoop Misra, published in The Lancet Regional Health – Southeast Asia (Feb 2026), is finally calling out what many good clinicians have quietly known: HbA1c alone is a shaky foundation for diagnosing or tracking diabetes here.

With over 101 million diabetics (and counting), relying on one number that's easily distorted by our unique biology isn't just imperfect — it can delay real problems by years or create unnecessary worry.

HbA1c vs OGTT: The Reality Check Table

OGTT (Oral Glucose Tolerance Test — fasting + 2-hour post 75g glucose) remains the most direct measure of how your body handles a sugar load right now.

Aspect	HbA1c	OGTT (Glucose Test)	Better Choice in India When...
Measures	Average sugar over 2-3 months (indirect)	Immediate glucose handling (direct)	Suspicion of anemia/G6PD
Fasting Required?	No	Yes (8-12 hrs)	-
Time Taken	5 min blood draw	2+ hours	Convenience matters
Affected by Anemia?	Yes — often falsely high	Minimal	Anemic patient
Affected by G6PD?	Yes — often falsely low	Minimal	Male, family history, tribal
Prediabetes Detection	Variable (misses or overcalls)	Gold standard for current impairment	Discordant results
Cost & Availability	Widely available, cheaper	Slightly more effort, available everywhere	Rural or lab limitations
Monitoring Control	Good if RBCs normal	Excellent for acute changes	Pregnancy, recent anemia fix

Real data from Indian studies: One large South India cohort (1,120 people) — OGTT caught prediabetes in 87.8% vs HbA1c's 45.4% (minimal overlap). Pune young adults study — HbA1c showed 23.3% prediabetes vs OGTT's 7.8%. Discordance is real, not theoretical.

What Exactly Does HbA1c Measure — And Where It Goes Wrong

HbA1c tells you the percentage of your hemoglobin that's sugar-coated over the past 2-3 months. It sounds perfect: no fasting, one blood draw, reflects long-term control.

Your red blood cells (RBCs) have a normal lifespan of about 120 days. HbA1c assumes steady production and normal survival. But anything that messes with RBC count, lifespan, shape, or turnover changes how much glucose gets "recorded" on them:

Iron deficiency anemia (super common) → falsely higher HbA1c. RBCs behave differently; glycation appears elevated even when average sugar is normal.
G6PD deficiency (genetic, X-linked, hits males harder) → shorter RBC lifespan → lower HbA1c. High sugar can be masked.
Hemoglobinopathies (thalassemia trait, sickle cell trait — prevalent in Punjab, Gujarat, tribal belts) → altered hemoglobin structure → unreliable readings.
Poorly standardized labs (still an issue outside big cities) add noise.

Correct the anemia, and HbA1c often drops 0.5-1.5 points. That's huge.

Why This Hits Us Harder Than the West (India-Specific Context)

Anemia isn't niche here. NFHS-5 data shows ~57% of women 15-49 and ~67% of children are anemic — many with iron deficiency. In several states, it's over 65-70%. G6PD deficiency ranges 2-6% nationally but spikes to 10-20%+ in tribal communities (Gonds, Bhils, Orissa pockets) and certain castes. Hemoglobin variants cluster regionally.

Western populations have far lower rates of these. That's why ADA/ADA guidelines work "okay" there but need heavy caveats for us. Public health surveys using only HbA1c? They risk painting a distorted picture of India's diabetes burden.

Delayed Diagnosis, Over-Diagnosis, Avoidable Worry

Imagine a man with undetected G6PD deficiency — his HbA1c stays "normal" while sugars climb silently. Diagnosis delayed 2-4 years. Complications creep in. Or the opposite: anemic woman labeled prediabetic for years, unnecessary meds, diet stress, family tension.

This isn't fear-mongering. It's daily reality in OPDs across Tier-2/3 cities and villages.

Practical Expert Checklist: Test Smarter, Not Harder

Use this before accepting any single number:

Step 1: Always get CBC (complete blood count) with Hb, MCV, RDW alongside HbA1c. High RDW (>15-17) or low Hb? Flag for further check.
Step 2: Screen for G6PD if male, family history, jaundice episodes, or from high-prevalence community (especially before primaquine/malaria drugs anyway).
Step 3: If anemia present — treat iron/folate first (3-6 months), repeat HbA1c.
Step 4: Discordance (high HbA1c but normal FPG/postprandial)? Do OGTT. Or vice-versa.
Step 5: For monitoring established diabetes — pair HbA1c with home glucose logs/fructosamine if RBC issues suspected.
Bonus: Consider CGM (continuous glucose monitoring) for 7-14 days in confusing cases — it doesn't lie.

This "multiparametric, risk-stratified" approach (as the Lancet piece advocates) is what sharp endocrinologists already follow.

Time to Move Beyond "HbA1c or Nothing"

After seeing the data and how it plays out in real patients, I'm convinced: HbA1c is a fantastic supporting actor, not the lead. In India, make OGTT + fasting glucose your primary tools for diagnosis, especially in younger people, anemic folks, or anyone from high-risk communities. Use HbA1c mainly for monitoring known diabetics whose blood picture is normal. Labs should ideally report "HbA1c (with caveat for anemia/hemoglobinopathy)".

This doesn't mean panic and abandon it. It means use it wisely. Better diagnosis today prevents heart, kidney, and eye trouble tomorrow.

FAQ

Q: Is HbA1c completely useless in India? No. It's useful when your hemoglobin is normal. Just don't bet everything on it alone.

Q: My lab says HbA1c 6.8%. Should I start metformin? Not yet. Check CBC, iron studies, do OGTT. Many such cases turn out normal after anemia correction.

Q: Which test is best during pregnancy? OGTT is preferred. HbA1c has different cutoffs and more interference.

Q: Can I just do fasting sugar only? It misses impaired glucose tolerance (post-meal spikes). OGTT catches more.

Q: How often should I retest after fixing anemia? 3 months minimum. RBC turnover takes time.

Q: Does this affect diabetes prevalence numbers? Yes. Pure HbA1c surveys likely overestimate prediabetes in iron-deficient groups and underestimate in G6PD hotspots.

Q: What about new tests like glycated albumin or fructosamine? Promising alternatives less affected by RBC lifespan — worth watching.

Know your numbers, but know your blood picture first. Your health deserves more than one imperfect test.