Fasting Insulin
A fasting insulin blood test measures the level of insulin in your blood after an overnight fast — a key early marker of insulin resistance.
Plain English
Patient-Friendly Explanation
Fasting insulin is a blood test, usually done in the morning after fasting, that measures how much insulin your pancreas needs to keep your blood sugar normal. If your body has become resistant to insulin, your pancreas has to pump out more of it — so a high fasting insulin level is often one of the earliest warning signs of insulin resistance, even before blood sugar rises.
Medical
Clinical Definition
Fasting insulin is measured after an 8–12 hour fast. In the presence of insulin resistance, beta-cell output rises to maintain euglycaemia, so elevated fasting insulin is an early marker of deteriorating glucose metabolism. Alongside HOMA-IR (calculated from fasting insulin × fasting glucose / 22.5), it is used to quantify insulin resistance in clinical and research settings. Reference ranges vary by assay and population, so interpretation requires clinical context. Hyperinsulinaemia is associated with visceral adiposity, dyslipidaemia and increased cardiometabolic risk.
Key Insight
Why It Matters
Fasting insulin can reveal insulin resistance years before blood sugar abnormalities appear — which is why Dr Joseph Wang includes it in comprehensive metabolic screening for patients with a family history of diabetes.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: August 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
