This site uses cookies to store information on your computer. I'm fine with this Cookie information
Follow is on Twitter Like us on Facebook Follow us on Instagram

We have started moving content to our new website at:

COVID-19 (Coronavirus info)

Information and guidance for public, NHSGGC staff, and community-based services.  Hospital visiting restrictions now in place.

Insulin C - peptide

Insulin C-peptide (connecting peptide), a 31 amino acid polypeptide, represents the midportion of proinsulin. During insulin secretion it is enzymatically cleaved from proinsulin and co-secreted in equimolar proportion with mature insulin. The half life of C-peptide is significantly longer than insulin, so it is detectable in higher concentrations and the level less variable. C-peptide is often a more reliable marker than insulin. In addition, insulin is destroyed by proteases in haemolysed samples, while C-peptide is not.

Clinical uses:

1. Insulinoma: elevated C-peptide levels from increased beta-cell activity

2. Covert self-administration of insulin: can be virtually ruled out as cause of hyperinsulinaemia by finding elevated C-peptide.

3. Type 1 diabetes mellitus: low C-peptide levels due to diminished insulin secretion, or suppressed as a normal response to exogenous insulin. Patients on insulin can develop anti-insulin antibodies which can interfere with insulin assay, so C-peptide can be used instead to check residual beta-cell activity.

Sample Requirements and Reference Ranges

Sample type  Plasma
Container  Lithium heparin
Precautions  Collect after overnight fast. Separate and freeze plasma.  Transport frozen.
Minimum volume  1 mL
Reference range Not applicable
Turnaround time  7 days
Method  Siemens Immulite
Quality Assurance
Last Updated: 13 October 2020