Several tests are used to diagnose and monitor glucose problems. They measure different things over different timeframes, which is why more than one is often used.
The tests
Fasting blood glucose — a snapshot after fasting, typically overnight. Simple and widely available; reflects one moment.
HbA1c — the proportion of haemoglobin with glucose attached, reflecting average glucose over roughly the preceding two to three months. Doesn't require fasting, and isn't affected by what you ate yesterday. Can be misleading in some conditions affecting red blood cells — anaemia, haemoglobinopathies, recent transfusion, kidney disease.
Oral glucose tolerance test (OGTT) — glucose measured before and after a standard glucose drink. Takes about two hours. More sensitive for detecting impaired glucose tolerance, and the standard test in pregnancy.
Random blood glucose — measured at any time; used mainly where symptoms are present.
Verify and insert: current Australian diagnostic thresholds for each test, for both prediabetes and diabetes, including whether a repeat confirmatory test is required.
Ongoing monitoring
Once diagnosed, HbA1c is the main marker of longer-term control, checked at intervals depending on stability and treatment.
Targets are individualised. A tighter target suits some people; a more relaxed one is appropriate for others, particularly where there's risk of hypoglycaemia or where other conditions dominate. A number that's right for one person can be inappropriate for another.
Verify: current Australian HbA1c target ranges and the circumstances for individualising them.
Monitoring extends beyond glucose, because complications are driven by more than it: blood pressure, lipids, kidney function, eye examination, foot assessment, and weight. Liver assessment is also relevant given how frequently the two coexist.
Continuous glucose monitoring
CGM uses a sensor to track glucose continuously, showing patterns that periodic testing misses — post-meal responses, overnight trends, time spent in range.
Well established in type 1 diabetes, and increasingly used in type 2 in specific circumstances. Subsidy arrangements differ by diabetes type and clinical situation.
Verify: current eligibility and subsidy arrangements.
Related: Type 2 diabetes explained · Diabetes care in Australia Next: Find a GP or diabetes service →
Educational information only. Not a substitute for medical advice — speak to a qualified health practitioner about your circumstances.