Prediabetes

Prediabetes is an intermediate state of glucose dysregulation in which glycaemia is above the normal range but below the threshold for diabetes. It identifies people at high risk of progressing to type 2 diabetes (about 5 to 10 percent per year) and at increased cardiovascular risk, and it is a window in which lifestyle change can prevent or delay diabetes.

• Diagnostic categories: HbA1c 42 to 47 mmol/mol (6.0 to 6.4 percent), or fasting plasma glucose 6.1 to 6.9 mmol/L (impaired fasting glucose), or 2-hour plasma glucose 7.8 to 11.0 mmol/L on a 75 g oral glucose tolerance test (impaired glucose tolerance). Some bodies use a lower HbA1c cut off of 39 mmol/mol (5.7 percent) and fasting glucose from 5.6 mmol/L.
• Risk factors: overweight or obesity (especially central), age over 40, family history of diabetes, South Asian, African-Caribbean, Black African or Middle Eastern ethnicity, previous gestational diabetes, polycystic ovary syndrome, hypertension, dyslipidaemia, sedentary lifestyle, severe mental illness, obstructive sleep apnoea, drugs (steroids, antipsychotics, statins mildly).
• Often asymptomatic, found by screening.

• Usually no symptoms. Occasionally fatigue, mild polyuria, postprandial sleepiness.
• Signs of insulin resistance: central adiposity, acanthosis nigricans (neck, axillae), skin tags, hirsutism.
• Associated features: hypertension, fatty liver, dyslipidaemia, sleep apnoea, polycystic ovary syndrome.
• Examination: weight, body mass index, waist circumference, blood pressure, skin.
• Red flags prompting investigation for diabetes: thirst, polyuria, weight loss, recurrent infections, blurred vision.

• HbA1c (not valid in haemoglobinopathy, recent blood loss or transfusion, iron or B12 deficiency, pregnancy, haemolytic anaemia, chronic kidney disease, so use glucose based tests there).
• Fasting plasma glucose after 8 hours fasting. Oral glucose tolerance test (75 g anhydrous glucose in 250 to 300 mL water, glucose at 0 and 2 hours) when HbA1c and fasting glucose are discordant or to confirm status.
• Repeat to confirm a borderline result in asymptomatic patients.
• Baseline tests for risk: lipid profile, liver function (ALT), creatinine and eGFR, urine albumin creatinine ratio, blood pressure.
• Differentials: stress hyperglycaemia, steroid effect, early diabetes, endocrine cause (Cushing syndrome, acromegaly), pancreatic disease, haemochromatosis.

Lifestyle (first line for all)

• Structured intensive lifestyle programme: aim for 5 to 10 percent weight loss in those who are overweight; this can reduce progression by over half.
• Diet: Mediterranean style or low-glycaemic-index diet, reduce refined carbohydrate, sugar sweetened drinks and saturated fat, increase fibre (30 g daily) and vegetables; consider low energy meal replacement programmes in obesity.
• Activity: at least 150 minutes per week of moderate aerobic exercise (brisk walking), plus resistance training twice weekly; reduce sitting time.
• Stop smoking; alcohol under 14 units per week.
• Sleep 7 to 8 hours; treat obstructive sleep apnoea.

Pharmacological (if lifestyle fails, or high risk such as BMI over 35, age under 60, previous gestational diabetes, rising HbA1c)

• Metformin immediate release 500 mg orally once daily with the evening meal, increased by 500 mg weekly to 1 g twice daily (or modified release 500 mg to 2 g once daily). Check eGFR before starting (avoid if eGFR below 30 mL/min/1.73 m2; reduce dose if 30 to 45) and B12 annually. Gastrointestinal side effects are common and usually transient. Hold during acute illness with dehydration and before contrast imaging.
• Where weight is the main driver and obesity is present, specialist supervised weight loss drugs such as semaglutide 2.4 mg subcutaneously weekly (started at 0.25 mg weekly and escalated every 4 weeks) or tirzepatide (2.5 mg weekly escalating by 2.5 mg every 4 weeks to 5 to 15 mg weekly) may be considered where local licensing allows.
• Do not use statins or antihypertensives solely for prediabetes; treat cardiovascular risk on its own merits.

Cardiovascular risk management

• Assess 10-year cardiovascular risk; offer atorvastatin 20 mg orally at night if risk is 10 percent or more (and for chronic kidney disease or type 1 diabetes if relevant); treat hypertension to target (below 140/90 mmHg clinic).

Special groups

• Women with previous gestational diabetes: annual HbA1c; high conversion risk; breastfeeding and lifestyle programme.
• Pregnancy: screen for gestational diabetes at 24 to 28 weeks with oral glucose tolerance test; metformin not recommended for prediabetes.
• Children and adolescents with obesity: lifestyle intervention; metformin only with paediatric specialist.
• Older adults: avoid overtreatment; focus on activity and weight preservation.

Follow up and referral

• HbA1c at least annually (6 monthly if higher risk or HbA1c above 46 mmol/mol); annual lipids and blood pressure.
• Refer to a structured diabetes prevention programme at diagnosis.
• Diagnose diabetes if HbA1c reaches 48 mmol/mol or more, or fasting glucose reaches 7.0 mmol/L or more, confirmed on repeat in an asymptomatic person.