Insulin is a hormone of the pancreas that opens the "door" for glucose into cells and lowers blood sugar. It is the main energy-storage hormone.
The problem begins when cells stop "hearing" it — insulin resistance develops. Then the pancreas makes more and more insulin, and its blood level rises long before sugar goes up.
Reference ranges
Approximate reference for fasting insulin:
| Fasting normal | about 2.6 – 11 µIU/mL |
| Optimal | closer to the lower bound |
| Read with glucose | to calculate the HOMA-IR index |
What an elevated level means
Elevated fasting insulin (while sugar is still normal) is an early sign of insulin resistance. The body compensates for the cells' "deafness" with an excess of the hormone.
Common causes and companions: excess weight and visceral fat, physical inactivity, excess sugar and refined carbohydrates, metabolic syndrome.
This is a reversible state: weight loss, movement and a diet lower in sugar reduce insulin and restore sensitivity to it.
What a low level means
Low fasting insulin in a healthy person is usually a good sign of high sensitivity to it. Very low insulin against a background of high sugar may point to type 1 diabetes (insufficient production) — a separate situation that requires a doctor.
How the test is done
Venous blood strictly fasting (8–12 hours), in the morning.
Test insulin together with glucose from the same sample — only then can the HOMA-IR index be calculated. The day before, avoid overeating and alcohol.
What affects the value
- Visceral fat — the main driver of insulin resistance and rising insulin.
- Movement — raises insulin sensitivity and lowers its level.
- Sugar and refined carbohydrates — raise insulin.
- Sleep and stress — lack of sleep and high cortisol worsen sensitivity.
- Eating before the test — sharply distorts the result.
Calculate using this marker
Calculators where Insulin is used directly:
Frequently asked questions
Why test insulin if sugar is normal?
Because insulin rises before sugar. With early insulin resistance the pancreas keeps glucose normal at the cost of excess insulin — and high fasting insulin catches the problem years earlier than a sugar test.
What is HOMA-IR?
It is an insulin-resistance index calculated from fasting insulin and glucose. It shows how "deaf" cells are to insulin. You can also assess your metabolic status without insulin using the METS-IR index — in our calculator.
How do you lower high insulin?
Weight loss (especially visceral fat), regular movement, less sugar and refined carbohydrates, and normal sleep. Insulin resistance is reversible, and insulin falls in step with lifestyle.