Fasting Insulin: what it means

Insulin is the hormone that moves sugar out of your blood and into cells. A fasting insulin measures how much your body is producing at rest. When cells resist insulin, the body compensates by making more — so a high fasting insulin with still-normal glucose can be an early sign of insulin resistance. Combined with fasting glucose, it forms the HOMA-IR estimate of insulin resistance.

Ranges vary by lab and aren't as standardized as glucose; lower fasting insulin generally reflects better insulin sensitivity. Interpretation is best done with your doctor.

Reference ranges differ between labs and are printed on your own report — always read your result against that range, not a general one.

• Insulin resistance, often with excess weight or metabolic syndrome
• A recent meal (this test should be fasting)

A high value is a starting point for a conversation, not a diagnosis — many causes are benign or temporary.

• Good insulin sensitivity
• In diabetes, a tired pancreas making less insulin

Fasting insulin can shift with diet, activity, and weight well before glucose does, so its trend is an early readout of metabolic change.

Discuss a high fasting insulin with your doctor as part of your metabolic picture, alongside glucose, A1c, and triglycerides.