Fasting insulin

What this test is

Fasting insulin is a blood test. It measures insulin after you have not eaten overnight. Some clinics use it, often with a formula called HOMA-IR, to look for early insulin resistance. That means your body needs more insulin than usual to keep blood sugar normal. This can happen years before diabetes shows up on other tests. But Canadian diabetes guidelines do not use fasting insulin to check your risk. They use two simpler tests instead: fasting blood sugar and A1c. These tests have clear evidence behind them. If you are worried about diabetes, those are the right tests to start with. They are also the tests we will use to plan next steps.