Prediabetes

Impaired glucose regulation short of diabetes — a high-risk state and an opportunity for prevention. Diagnostic thresholds are shared with Diabetes – diagnosis.

Definition

Prediabetes covers two overlapping states, either of which raises future diabetes and cardiovascular risk:

• Impaired fasting glucose (IFG) — fasting venous glucose 6.1–6.9 mmol/L.
• Impaired glucose tolerance (IGT) — 2-hour OGTT glucose 7.8–11.0 mmol/L.

An HbA1c of 6.0–6.4% (42–46 mmol/mol) is also widely used to identify a high-risk group, though HbA1c is a less sensitive screen than an OGTT for IGT. About 30% of Australians with impaired glucose tolerance progress to diabetes within 10 years, so prediabetes is a call to act — but not in itself an indication to start glucose-lowering medication.

Who to test

Use AUSDRISK to identify candidates, then confirm with fasting glucose, HbA1c, or OGTT. Higher-risk groups (as for type 2 screening): age >40 (>18 in Aboriginal and Torres Strait Islander people), first-degree family history, overweight/obesity, previous gestational diabetes, PCOS, and long-term corticosteroid or antipsychotic use.

Management

Lifestyle intervention is first-line and the most effective step:

• Weight loss of 5–10% of body weight where overweight/obese.
• Physical activity — at least 150 min/week of moderate aerobic activity plus resistance training.
• Dietary change — reduced refined carbohydrate and energy intake; structured programs and dietitian involvement improve adherence.

Intensive lifestyle programs reduce progression to diabetes by roughly half.

Metformin may be considered in addition to lifestyle for higher-risk individuals — for example a BMI >35, age <60, previous gestational diabetes, or rising HbA1c despite lifestyle change — though it is less effective than lifestyle change and is not PBS-subsidised for prediabetes.

Monitor by re-checking fasting glucose/HbA1c at least annually to detect progression, and manage concurrent cardiovascular risk factors (blood pressure, lipids, smoking).