Prediabetes
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Direct answer
Prediabetes is the zone of dysglycaemia short of diabetes — impaired fasting glucose (IFG), impaired glucose tolerance (IGT), or an HbA1c of 5.7–6.4% — and it identifies people at high risk of progressing to type 2 diabetes at roughly 5–10% per year. The Diabetes Prevention Programme showed that intensive lifestyle change (7% weight loss, 150 minutes of weekly activity) cut progression by 58%, versus about 31% with metformin. Management is therefore lifestyle-first, with metformin reserved for younger, more obese patients and those with prior gestational diabetes. Per ICMR-INDIAB estimates, roughly one in seven Indian adults already sits in this zone, so detection and prevention are national priorities.
What you must remember
- Definitions: IFG — fasting plasma glucose 100–125 mg/dL (ADA; WHO uses 110–125); IGT — 2-hour OGTT value 140–199 mg/dL; ADA HbA1c band 5.7–6.4%.
- Progression to diabetes runs about 5–10% per year overall; IGT plus IFG together carry the highest risk.
- Diabetes Prevention Programme: lifestyle 58% risk reduction, metformin 31%, versus placebo — lifestyle wins and was most effective in the over-60s.
- Metformin suits those under 60, BMI ≥35 kg/m2, prior gestational diabetes, or rising HbA1c despite lifestyle effort.
- Screen with fasting glucose, HbA1c or OGTT; if normal, rescreen at least every 1–3 years (annual if multiple risk factors).
- Indians develop dysglycaemia at lower BMI — the "thin-fat" phenotype with central adiposity — so waist circumference and family history matter more than weight alone.
- Cardiovascular risk, not just glycaemia, drives outcomes: blood pressure, lipids and tobacco need equal attention.
- Post-OGTT 2-hour glucose predicts cardiovascular events better than fasting glucose — an examinable epidemiological point.
Numbers worth knowing, and how to use them
A 42-year-old Indian man, BMI 26 kg/m2, waist 96 cm, father on insulin, fasting glucose 114 mg/dL, HbA1c 6.0%. He has IFG with HbA1c in the prediabetic band. The next question is whether he also has IGT, which changes both risk and vigilance — a 75 g OGTT with a 2-hour value of 168 mg/dL confirms it. His combined IFG-plus-IGT status places his annual conversion risk near the top of the range, so intervention now is not cosmetic medicine.
Write the prescription in order. First, 150 minutes/week of moderate activity (brisk walking qualifies) plus resistance work twice weekly, with a target of 7% body-weight loss — for him that is under 6 kg. Second, dietetic structure: cut refined carbohydrate, sugary drinks and deep-fried snacks; the Indian plate's glycaemic load from white rice is a legitimate counselling target, with whole grains, pulses and legumes as substitutes. Third, review at 3–6 months: if HbA1c climbs past 6.0–6.2% despite genuine effort, or if he is younger and heavier than our man, add metformin 500 mg daily titrated to 1 g twice daily. Fourth, treat the whole risk — his blood pressure of 138/88 and LDL need their own plan.
Keep two long arcs in mind: prediabetes is reversible but recurrent, so screening never really stops; and a small proportion of adult "prediabetics" actually have slowly progressing type 1 (LADA) or MODY — suspect these when the patient is lean, without metabolic syndrome, or has a strong three-generation family history, and check antibodies or refer rather than simply escalating metformin.
How the exam frames it
Question-writers test three seams. The first is definition drift between ADA and WHO fasting cutoffs (100 versus 110 mg/dL) — quote the ADA figure and note the WHO alternative. The second is trial arithmetic: 58% and 31% from the Diabetes Prevention Programme are quoted directly in stems, so they must be exact. The third is the metformin-indication vignette: a 52-year-old with BMI 38 and past gestational diabetes is the textbook candidate, whereas a thin 70-year-old with BMI 22 is not. A favourite distractor asks which drug is licensed specifically to "prevent diabetes" — in most guidelines, including Indian practice, metformin alone holds that place, and acarbose (with modest DPP evidence) is a niche answer.
Frequently asked questions
What are the diagnostic criteria for prediabetes?
Fasting plasma glucose 100–125 mg/dL (ADA) or 110–125 mg/dL (WHO), 2-hour OGTT glucose 140–199 mg/dL, or HbA1c 5.7–6.4%. Any one criterion establishes the diagnosis.
Which intervention best prevents progression to diabetes?
Structured lifestyle modification — approximately 7% weight loss with at least 150 minutes weekly of moderate exercise — reducing incidence by 58% in the Diabetes Prevention Programme, outperforming metformin's 31%.
When should metformin be used in prediabetes?
For adults under about 60 with BMI ≥35, prior gestational diabetes, or progressive dysglycaemia despite lifestyle attempts. It is an adjunct, never a replacement for lifestyle prescription.
Why is prediabetes especially consequential in Indians?
South Asians develop dysglycaemia at lower BMI and younger ages (the thin-fat Indian phenotype), and national survey data suggest a very large prediabetic pool, so early detection and prevention have outsized public-health value.
How often should a person with prediabetes be screened?
At least annually once identified — with fasting glucose or HbA1c — because conversion is silent; those with additional risk factors warrant tighter review and cardiovascular risk assessment.