What Is Fasting Insulin?
Fasting insulin measures the amount of insulin in your bloodstream after an overnight fast. It's one of the earliest indicators of insulin resistance — the metabolic dysfunction at the root of type 2 diabetes, obesity, fatty liver disease, and cardiovascular disease.
The critical point: fasting insulin rises years to over a decade before blood sugar becomes abnormal.
How Insulin Works
When you eat carbohydrates, your blood glucose rises. Your pancreas releases insulin, which signals cells to absorb that glucose. Insulin resistance develops when cells stop responding efficiently. The pancreas compensates by producing more insulin.
Why Your Annual Physical Misses This
Standard bloodwork tests fasting glucose and sometimes HbA1c — both measure blood sugar, not insulin. Fasting insulin catches insulin resistance at the earliest stage, years before glucose becomes abnormal.
Normal Fasting Insulin Levels
Below 5 mU/L: Optimal. 5–10: Normal. 10–15: Borderline elevated. Above 15: Elevated — insulin resistance likely. Above 25: Significant insulin resistance.
How to Improve Fasting Insulin
- Reducing refined carbohydrates and added sugar
- Resistance training — builds insulin-sensitive muscle tissue
- Aerobic exercise — walking after meals reduces postprandial insulin
- Improved sleep
- Reducing visceral fat
Is Fasting Insulin Tested in Standard Care?
No. Stem Health includes fasting insulin and HOMA-IR in every Core and Horizon Assessment.
