Prediabetes: The Warning Stage You Can Still Reverse
Prediabetes is the least discussed and most useful diagnosis in metabolic medicine. Blood sugar is higher than normal but has not reached the diabetes threshold, and at this point the underlying process is still substantially reversible.
The numbers that define it
Three tests are used, and any one can establish it:
- Fasting plasma glucose: 100-125 mg/dL, against a normal below 100 and diabetes at 126 or above
- HbA1c: 5.7-6.4 percent, against a normal below 5.7 and diabetes at 6.5 or above
- Two-hour value on an oral glucose tolerance test: 140-199 mg/dL
HbA1c reflects the average over roughly the previous three months, which makes it the most practical single test. It can be misleading in anaemia, after a transfusion, in pregnancy and in some haemoglobin variants, so a fasting glucose is a useful cross-check.
Why it rarely causes symptoms
Classic diabetes symptoms, meaning excessive thirst, frequent urination and unexplained weight loss, appear only when glucose is high enough to spill into urine. Prediabetes sits well below that level, so almost everyone feels normal.
A few clues sometimes appear: velvety dark thickening of the skin at the back of the neck, armpits or groin, called acanthosis nigricans; skin tags; recurrent fungal infections; and worsening fatigue after heavy carbohydrate meals.
What is actually happening
Muscle, liver and fat cells respond less well to insulin. The pancreas compensates by producing more of it, and for years that compensation keeps glucose almost normal. Prediabetes is the point where compensation starts to fail. Insulin-producing beta cells are still largely intact, which is precisely why intervention at this stage works so well.
Who is at highest risk
- Family history of type 2 diabetes in a parent or sibling
- Excess weight, especially around the abdomen
- Waist above roughly 90 cm in men or 80 cm in women for South Asian populations
- Physical inactivity
- Age above 35, though onset is increasingly earlier
- Previous gestational diabetes, or a baby over 4 kg at birth
- Polycystic ovary syndrome
- High triglycerides or low HDL cholesterol
- Untreated obstructive sleep apnoea
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South Asians develop insulin resistance at lower body mass index values than European populations, so screening should not wait for obvious obesity.
What the evidence says about reversing it
Large trials, including the Diabetes Prevention Program and the Indian Diabetes Prevention Programme, tested lifestyle change against medication and against no intervention. Structured lifestyle change reduced progression to diabetes by roughly half to two thirds, and outperformed metformin in most groups. The benefit persisted for years after the programme ended.
The core components were modest and achievable: about 7 percent body weight loss and 150 minutes of moderate activity a week.
A practical plan
Movement. Aim for 30 minutes of brisk walking five days a week, plus two sessions of resistance work. Muscle takes up glucose without needing much insulin, so building and using it directly improves the problem. Breaking up long sitting with a few minutes of walking every hour has its own independent effect.
Carbohydrate quality. You do not need to eliminate carbohydrate, but shift it. Replace refined grains, sweetened drinks and biscuits with whole grains, millets, legumes, vegetables and nuts. Adding protein, fat or fibre to a carbohydrate meal blunts the glucose rise. Eating vegetables and protein before the rice or roti in the same meal measurably lowers the peak.
Weight. Losing 5-7 percent of body weight is the single strongest lever. For an 80 kg person that is 4-6 kg, not a transformation.
Sleep. Fewer than six hours a night worsens insulin sensitivity within days. Treat snoring with daytime sleepiness as a medical issue, not a habit.
Alcohol and tobacco. Both worsen the trajectory, and tobacco in any form independently raises diabetes risk.
Medication
Metformin is sometimes offered, particularly with a body mass index above 35, age below 60, or previous gestational diabetes. It is a reasonable adjunct, not a substitute for the lifestyle work.
Follow-up
Repeat HbA1c or fasting glucose once a year, or every six months if your values sit at the upper end. Also check blood pressure and a lipid panel, because the same insulin resistance drives those too.
Prediabetes is not a diagnosis to file away. It is a time-limited window, and what you do in the next year or two matters more than what you do in the year after a diabetes diagnosis. Discuss testing and targets with a doctor.