Glossary term

Fasting insulin

Picks up insulin resistance 2-5 years before A1c shifts. Target under 8 uIU/mL. Over 10 flags a workup.

Fasting insulin, drawn after 10-12 hours without food, measures how much insulin your pancreas has to release to keep glucose steady. Reference ranges run roughly 2.6-24.9 uIU/mL, but insulin resistance starts well inside the "normal" band. Functional target is under 8 uIU/mL; values 10+ warrant a workup even with a normal A1c. Paired with fasting glucose, it generates HOMA-IR - an earlier insulin-resistance read than A1c. Insulin often shifts 2-5 years before glucose does. Included in the Advanced panel and a required screen before GLP-1.

Unit

uIU/mL

Typical range

Reference ~2.6-24.9 uIU/mL; functional target < 8; workup over 10.

Medically reviewed byDr. Lena Okafor, MD

Medical Director - updated April 2026 - How we review