Fasting Insulin Test
A blood test that measures insulin after fasting, sometimes used to estimate insulin resistance.
Quick Summary
To assess insulin resistance (HOMA-IR) in PCOS or metabolic problems, and investigate low blood sugar.
Fasting insulin, often with fasting glucose.
Fast for 8–12 hours.
Overview
Results vary a lot between labs.
It isn't needed to diagnose diabetes.
What It Measures
Insulin
Fasting level.
HOMA-IR
Calculated insulin resistance.
How It's Performed
- 01
Preparation
Usually no special preparation unless your doctor advises.
- 02
Blood sample
A small amount of blood is taken from a vein in your arm.
- 03
Afterwards
Press on the spot; a small bruise is common.
Interpreting Results & Next Steps
Discuss with Doctor
Normal ranges differ between laboratories; use the range on your report. Your doctor will explain what your result means and what happens next.
If values are High:
High fasting insulin suggests insulin resistance.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Insulin in Blood Test(opens in a new tab) · MedlinePlus, US National Library of Medicine