Skip to content

C-Peptide

Published: July 27, 2026Updated: August 25, 2026

C-peptide is a byproduct produced during the conversion of proinsulin to insulin, reflecting the body's endogenous insulin production.

Quick summary

C-peptide measures the body's insulin production.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
ng/mL
Clinical utility
diagnostic
Result kind
quantitative
FDA-cleared
Roche C-Peptide, Abbott C-Peptide, Siemens C-Peptide
interpretation: {"text":"May indicate type 1 diabetes, exogenous insulin use, or hypoinsulinemia.","label":"Low C-Peptide"}; {"text":"May suggest insulin resistance, insulinoma, or hyperinsulinemia.","label":"High C-Peptide"}

C-peptide is a 31-amino-acid polypeptide that is cleaved from proinsulin during the formation of insulin. It is released into the bloodstream in amounts equimolar to insulin, making it a useful marker for endogenous insulin production.

The measurement of C-peptide levels is particularly valuable in distinguishing between type 1 and type 2 diabetes, as well as in evaluating insulinoma and other conditions related to insulin production.

Normal C-peptide levels range from 0.8 to 3.1 ng/mL. Elevated levels may indicate insulin resistance or insulinoma, while low levels may suggest type 1 diabetes or exogenous insulin use.

Frequently asked questions

What is the normal range for C-peptide?
The normal range for C-peptide is typically between 0.8 and 3.1 ng/mL.
Why is C-peptide measured?
C-peptide is measured to assess endogenous insulin production, differentiate between type 1 and type 2 diabetes, and diagnose conditions like insulinoma.
  1. 1
    C-Peptide - Lab Tests OnlineSource
  2. 2
    National Institute of Diabetes and Digestive and Kidney DiseasesSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy