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Endocrinology & Metabolic

Prediabetes (Non-diabetic Hyperglycaemia)

Non-diabetic hyperglycaemia, often called prediabetes, is glucose above the usual range but below the diagnostic threshold for diabetes; it identifies increased type 2 diabetes and cardiovascular risk and is an opportunity for intensive prevention.

In a nutshell

Non-diabetic hyperglycaemia, or prediabetes, means HbA1c 42 to 47 mmol/mol or fasting plasma glucose 5.5 to 6.9 mmol/L in the NICE prevention pathway. It is usually asymptomatic but signals increased diabetes and cardiovascular risk. Offer intensive lifestyle prevention first, consider metformin selectively when risk worsens or lifestyle support is not possible, and reassess at least annually.

Classic presentation

An asymptomatic adult with overweight or central adiposity and an HbA1c in the non-diabetic-hyperglycaemia range found at a health check.

Key points

  • The practical UK prevention thresholds are HbA1c 42 to 47 mmol/mol or fasting glucose 5.5 to 6.9 mmol/L.
  • Diagnostic diabetes begins at HbA1c 48 mmol/mol or fasting glucose 7.0 mmol/L, with confirmation when asymptomatic.
  • Lifestyle prevention is first-line and more effective than relying on metformin alone.
  • Metformin is selective, not automatic; consider it when results worsen despite lifestyle change or lifestyle participation is not possible.
  • Treat blood pressure, lipids, smoking, weight and other cardiovascular risks in parallel.

First-line investigation

HbA1c, or fasting plasma glucose if HbA1c is unreliable, with symptoms and cardiovascular-risk assessment.

Management

Exclude diabetes and acute illness

  • Check for osmotic symptoms, weight loss, ketones, dehydration or diabetic-range results; use the diabetes or acute hyperglycaemia pathway when present.2

Confirm and risk-stratify

  • Confirm the result with HbA1c or fasting plasma glucose, assess test reliability, then measure blood pressure, lipids, weight/central adiposity and comorbidities.1,3

Prevent progression

  • Offer intensive structured lifestyle-change support with weight, diet, physical-activity and behaviour goals.1,5

Treat wider risk

  • Manage hypertension, dyslipidaemia, smoking, obesity, CKD and fatty liver through their own prevention and treatment pathways.3,5

Use metformin selectively

  • Consider metformin when glycaemia deteriorates despite intensive lifestyle change or lifestyle participation is not possible, especially with higher BMI, after renal and BNF checks.1,4

Repeat at-risk monitoring

  • For high-risk results, repeat blood testing and lifestyle review at least annually, with earlier review if risk or symptoms increase.1

Exam traps

  • Do not call symptomatic diabetic-range hyperglycaemia prediabetes.
  • HbA1c can be unreliable in altered red-cell turnover, haemoglobinopathy, recent blood loss/transfusion and pregnancy.
  • An asymptomatic diabetic-range HbA1c needs confirmation through the appropriate diagnostic pathway.
  • Metformin does not replace intensive lifestyle change and needs renal-function and BNF checks.
  • Non-diabetic hyperglycaemia also signals cardiovascular risk.

Key sources

  1. NICE PH38: Type 2 diabetes: prevention in people at high risk (NICE pathway for risk identification, HbA1c/fasting-glucose thresholds, intensive lifestyle change, selective metformin and repeat assessment; published 12 July 2012, updated 15 September 2017 and accessed 4 August 2026.)Updated 15 Sept 2017
  2. NICE NG28: Type 2 diabetes in adults: management (Current NICE diagnostic and management pathway used when hyperglycaemia reaches the diabetic range; current page accessed 4 August 2026.)
  3. NICE NG238: Cardiovascular disease: risk assessment and reduction, including lipid modification (Current NICE recommendations on QRISK3, lifestyle, statin decisions, blood pressure/lipid risk factors and follow-up; accessed 4 August 2026.)
  4. British National Formulary (BNF) (Current UK prescribing information for metformin and related diabetes-prevention or cardiovascular medicines; product-specific dose, renal, interaction and monitoring details must be checked at the point of care; accessed 4 August 2026.)
  5. NICE NG246: Overweight and obesity management (Current NICE recommendations on central adiposity, behavioural weight management and relevant obesity services; accessed 4 August 2026.)

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.