Prediabetes: The Window Before Diabetes, and How to Use It

Prediabetes means blood glucose is above normal but below the threshold for diabetes. It is frequently reported on a health check, mentioned briefly, and forgotten. That is the most consequential missed opportunity in metabolic medicine, because this is the one stage where the trajectory can still be turned around.

The numbers

• Fasting glucose 100-125 mg/dL (impaired fasting glucose)
• HbA1c 5.7-6.4%
• Two-hour glucose 140-199 mg/dL on an oral glucose tolerance test (impaired glucose tolerance)

Above these ranges is diabetes; below is normal.

The oral glucose tolerance test detects more cases than fasting glucose alone, because in South Asians post-meal glucose often rises before fasting glucose does. Someone with a normal fasting sugar can still have impaired glucose tolerance.

Why it matters more than it sounds

• Roughly 5-10% of people with prediabetes develop type 2 diabetes each year, and a large majority eventually do without intervention
• Damage to blood vessels and nerves begins in the prediabetes range, not at the moment of diagnosis. Retinopathy and neuropathy are already detectable in some people with prediabetes.
• Cardiovascular risk is already elevated
• In South Asians, progression tends to be faster and to occur at lower body weights

Who should be tested

• Everyone from about age 30 in Indian populations
• Earlier with BMI above 23 plus another risk factor
• Family history of diabetes in a parent or sibling
• History of gestational diabetes, which carries a very high lifetime risk
• PCOS
• High blood pressure, abnormal lipids or fatty liver
• Central obesity, waist above 90 cm in men or 80 cm in women

What the evidence shows actually works

This is one of the best-studied areas in prevention, and the results are unusually clear.

Lifestyle intervention reduces progression to diabetes by around 50-58% in major trials, including the Indian Diabetes Prevention Programme. That is a larger effect than metformin achieved in the same trials, and the benefit persisted for years after the programme ended.

The components that produced it:

• Weight loss of 5-7% of body weight
• 150 minutes a week of moderate physical activity
• Reduced calorie and fat intake, with more fibre

Notably, in the Indian programme, benefit was seen even without much weight loss, which suggests activity and diet quality matter in their own right for South Asian populations.

Practical changes with the largest effect

• Cut sugar-sweetened drinks and sweets first; these give the fastest improvement
• Reduce the portion of refined carbohydrate — white rice, maida, biscuits — rather than eliminating carbohydrate
• Replace some refined grain with whole grain, millets, or pulses
• Increase protein and vegetables at each meal
• Walk 10-15 minutes after meals; this blunts post-meal glucose measurably
• Add resistance training twice a week, since muscle is the main site of glucose disposal
• Prioritise sleep; short sleep worsens insulin sensitivity within days

Medication

Metformin is considered in people at highest risk — younger age, BMI above 35, previous gestational diabetes, or HbA1c at the top of the prediabetes range — and where lifestyle change has not been enough. It is an adjunct, not a replacement.

What to monitor

• HbA1c or fasting glucose annually, more often if at higher risk
• Blood pressure
• Lipid profile
• Weight and waist circumference
• Liver assessment if fatty liver is present

What not to do

• Do not treat it as nothing. “Borderline sugar” is a diagnosis, not a reassurance.
• Do not rely on supplements, karela juice, methi or similar as the strategy. Some may have a small effect; none replaces weight, activity and diet change.
• Do not wait for symptoms. There are none at this stage.

When to see a doctor

• Any result in the prediabetes range, to plan a structured approach
• Symptoms of diabetes: increased thirst, frequent urination, unexplained weight loss, blurred vision
• Previous gestational diabetes, for annual screening
• Family history with no testing done

This article is general health information. Screening intervals and any medication decisions should be discussed with your doctor.