C-Peptide Test
A blood test that shows how much insulin your body is making.
Quick Summary
To help tell type 1 from type 2 diabetes and investigate low blood sugar.
C-peptide level.
Fasting may be advised.
Overview
C-peptide is released with the body's own insulin, not injected insulin.
Low levels suggest type 1 diabetes.
What It Measures
C-peptide
Insulin production.
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 Low:
Low levels suggest little insulin production.
If values are High:
High levels can occur with insulin resistance.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- C-Peptide Test(opens in a new tab) · MedlinePlus, US National Library of Medicine