Insulin is the hormone the beta cells of the pancreas release to move glucose out of the blood and into muscle, liver and fat tissue. Measured after an overnight fast, it shows how much hormone the pancreas needs to keep fasting glucose where it is. It speaks for the insulin-signalling side of carbohydrate metabolism rather than for sugar levels themselves.
No readings for this marker yet.
Raised fasting insulin most often reflects insulin resistance, where tissues respond weakly and the pancreas compensates by secreting more; it also accompanies excess weight, metabolic syndrome and polycystic ovary syndrome. Low values most often point to reduced beta-cell output, as in long-standing or type 1 diabetes, and are sometimes simply seen in lean, insulin-sensitive people. Insulin is not read as a verdict on its own — the same number means different things depending on the glucose beside it. One unexpected result is a reason to repeat the test and discuss it with a doctor.
The test requires a genuine overnight fast: any food, sweetened drink or even coffee with sugar in the preceding hours raises it, and recent exercise or acute illness shifts it in either direction. Exogenous insulin therapy and drugs that stimulate secretion distort the reading, which is why C-peptide is preferred in treated patients. Insulin is interpreted with fasting glucose, from which HOMA-IR is calculated, and alongside HbA1c and C-peptide.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.