GPAtlas🧭 When to suspect (and when to screen)
Non-diabetic hyperglycaemia (NDH) – commonly called prediabetes, and historically impaired fasting glucose or impaired glucose tolerance – is a blood glucose above normal but below the diabetic range. NICE PH38 defines it as a glycated haemoglobin (HbA1c) of 42–47 mmol/mol (6.0–6.4%) or a fasting plasma glucose (FPG) of 5.5–6.9 mmol/L. It is usually asymptomatic, found incidentally or through structured risk screening.
NDH matters for two reasons: it carries a high risk of progression to type 2 diabetes mellitus (T2DM), and it is a marker of raised cardiovascular disease (CVD) risk. Crucially, it is often reversible. The key skills in primary care are to confirm the band, refer to structured lifestyle support, manage the whole cardiovascular risk, and recognise when the result has actually crossed into diabetes.
| HbA1c | Classification | Action |
|---|---|---|
| < 42 mmol/mol (< 6.0%) | Normal | Lifestyle advice; reassess by risk (low risk 5-yearly, moderate 3-yearly) |
| 42–47 mmol/mol (6.0–6.4%) | Non-diabetic hyperglycaemia (high risk) | Refer to the NHS Diabetes Prevention Programme; annual HbA1c + weight check |
| 44–47 mmol/mol (6.2–6.4%) or FPG 6.5–6.9 | Highest-risk subgroup | Prioritise for the intensive lifestyle programme where places are limited |
| ≥ 48 mmol/mol (≥ 6.5%) | Diabetes range | Asymptomatic → repeat to confirm; symptomatic → diagnose now; manage as T2DM (NG28) |
Raise suspicion and offer a blood test in those with risk factors: overweight or obesity (body mass index [BMI] ≥ 25, or ≥ 23 if South Asian or Chinese) and central adiposity, physical inactivity, age ≥ 40 (or ≥ 25 in South Asian, Chinese, African-Caribbean and black African groups), a first-degree family history of T2DM, previous gestational diabetes mellitus (GDM), polycystic ovary syndrome (PCOS), hypertension, established CVD, non-alcoholic fatty liver disease (NAFLD), or treatment with antipsychotics. Use a validated tool (e.g. the Diabetes UK Know Your Risk score) to direct who to test.
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🧠 Clinical pearl Read the result, not just the band. A single asymptomatic HbA1c of ≥ 48 mmol/mol is not a diabetes diagnosis – it must be repeated before labelling. But the same ≥ 48 with osmotic symptoms (thirst, polyuria, weight loss) is diabetes: diagnose and act on the single result, do not wait for a repeat. |
Source: NICE PH38 · NHS Diabetes Prevention Programme
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