Prediabetes (Non-Diabetic Hyperglycaemia)
Blood glucose above normal but below the diabetes threshold — a reversible warning state.
Overview
Prediabetes is HbA1c 42–47 mmol/mol (6.0–6.4%) or fasting glucose 5.5–6.9 mmol/L. Around 5–10% of people with prediabetes develop type 2 diabetes each year, but structured lifestyle programmes reduce that risk by more than half.
Symptoms
- • Usually asymptomatic — detected on routine screening
- • Sometimes mild thirst, tiredness, frequent urination
- • Skin tags or acanthosis nigricans (dark velvety patches in skin folds)
Risk factors
- • BMI ≥25 (≥23 in South Asian, African, Caribbean ancestry)
- • Family history of type 2 diabetes
- • History of gestational diabetes or PCOS
- • Age ≥40 (≥25 in higher-risk ethnicities)
- • Hypertension or dyslipidaemia
Causes
- • Insulin resistance driven by excess visceral fat
- • Genetic predisposition
- • Sedentary lifestyle and ultra-processed diet
🚨 Red flags — seek urgent care
- • Unintentional weight loss with thirst and polyuria — check for overt diabetes
- • Symptoms of cardiovascular disease
When to seek care
- • HbA1c result in the prediabetes range
- • Multiple risk factors and no recent screening
- • Difficulty making lifestyle changes alone
Diagnosis
- • HbA1c 42–47 mmol/mol (6.0–6.4%) on two occasions, or
- • Fasting plasma glucose 5.5–6.9 mmol/L, or
- • 2-hour OGTT 7.8–11.0 mmol/L (impaired glucose tolerance)
- • Reassess annually with HbA1c
Treatment
- • Structured lifestyle programme (NHS Diabetes Prevention Programme or equivalent)
- • 5–10% body-weight loss; Mediterranean or low-carb dietary pattern
- • ≥150 minutes/week moderate activity plus 2 resistance sessions
- • Metformin considered in BMI ≥35 or progressive HbA1c despite lifestyle change
- • Address co-existing hypertension and dyslipidaemia
Prevention
- • Maintain healthy weight and waist circumference
- • Active lifestyle and good sleep
- • Limit ultra-processed food and sugary drinks
Complications
- • Progression to type 2 diabetes
- • Cardiovascular disease risk already elevated
- • Non-alcoholic fatty liver disease
Prognosis
Around 30–50% of people return to normal glucose with sustained lifestyle change. Even without full reversal, intensive lifestyle change halves diabetes incidence over 3 years.
Education & self-care
Prediabetes is a wake-up call, not a diagnosis. Small, sustained changes in diet, movement and weight measurably reduce future risk.
Frequently asked questions
Will I definitely get diabetes?
No. With structured lifestyle change most people delay or avoid diabetes entirely.
Should I take metformin?
Lifestyle change is first-line. Metformin is considered when HbA1c keeps rising despite lifestyle, or in high-risk groups.
Will I definitely develop diabetes?
Without intervention, around a third of people with prediabetes progress to type 2 diabetes within 5 years. A structured lifestyle programme reduces that risk by more than half.
Does metformin help in prediabetes?
Yes — it reduces progression by about 30%, less than lifestyle change alone but useful in higher-risk groups (BMI >35, age <60, history of gestational diabetes) under specialist guidance.
Which lifestyle changes matter most?
Modest weight loss (5–7%), 150 minutes a week of moderate activity, reducing ultra-processed food and sugary drinks, and good sleep collectively have the largest effect.