Fasting glucose (fasting blood sugar)

Your blood sugar first thing, before eating — a quick snapshot of how your body handles glucose.

What it measures

The concentration of glucose in your blood after an overnight fast.

Why it matters

Lower-normal fasting glucose tracks with better metabolic health and lower mortality. Rising values are an early warning on the road toward type-2 diabetes.

Healthy target

3.9–5.0 mmol/L

How to read your value

It’s a single moment in time and can be nudged up by stress, poor sleep or illness. HbA1c and fasting insulin give a fuller picture.

What can affect it

• Recent carbohydrate intake, sleep and stress
• Physical activity improves it
• Body weight and insulin resistance
• Some medications (e.g. steroids) raise it

Does the target differ by age or sex?

Same target for men and women across adulthood. Pregnancy has its own, lower thresholds.

When to talk to a clinician

A high fasting glucose should be confirmed and interpreted by a clinician — usually with HbA1c and a repeat test — before any label or treatment.