Is my Fasting Insulin normal?
Free blood test checker · Standard + longevity-optimal ranges
What is a normal Insulin level?
Fasting insulin is one of the earliest markers of metabolic dysfunction. Insulin can be elevated for years before fasting glucose or HbA1c become abnormal. Optimal fasting insulin is below 6 uIU/mL. Above 10 suggests insulin resistance. Combined with fasting glucose, it calculates HOMA-IR, the best simple measure of insulin resistance.
| Range | Values |
|---|---|
| Standard Reference | 2–25 uIU/mL |
| Optimal | 2–6 uIU/mL |
| Longevity Optimal | < 6 uIU/mL |
| High Risk | > 25 uIU/mL |
What causes abnormal Insulin levels?
Elevated fasting insulin is caused by insulin resistance from excess body fat (especially visceral fat), sedentary lifestyle, high refined carbohydrate and sugar diet, chronic stress, poor sleep, PCOS (in women), and genetic predisposition. It's also elevated in early type 2 diabetes when the pancreas overproduces insulin to compensate for resistance.
When should you see a doctor?
See your doctor if fasting insulin is above 10 uIU/mL, especially with other metabolic risk factors (high triglycerides, low HDL, abdominal obesity, high blood pressure). Request HOMA-IR calculation. If insulin is above 15 uIU/mL, discuss a formal glucose tolerance test and metabolic syndrome screening.
Insulin and longevity
Fasting insulin may be the single most underutilized biomarker in standard medicine. Insulin resistance — detectable via elevated fasting insulin years before glucose or HbA1c become abnormal — is the root driver of metabolic syndrome, type 2 diabetes, MASLD (fatty liver), PCOS, and is increasingly linked to Alzheimer's disease ("type 3 diabetes"). HOMA-IR (fasting insulin × fasting glucose / 405) below 1.0 is considered optimal for longevity. The fact that fasting insulin is not included in standard metabolic panels means most insulin resistance goes undetected until organ damage has already begun. Exercise is the most potent insulin sensitizer — a single bout of resistance training improves insulin sensitivity for 24-48 hours.
Where to get a Insulin test
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Related biomarkers
These biomarkers are often tested alongside Insulin for a more complete picture.
Frequently asked questions
What is a normal fasting insulin level?
Why doesn't my doctor test fasting insulin?
What is HOMA-IR?
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Sources: Reference ranges based on AHA/ACC, ADA, and AACE clinical guidelines. Biological variation data from Ricos/Westgard database. Longevity-optimal ranges reflect targets used by preventive and functional medicine practitioners.
Last reviewed: April 2026. This tool provides general health information and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider about your specific results.