C-peptide (Serum or Plasma, Mass Concentration)

Why is this test done?

Doctors may order a C-peptide test to diagnose or monitor conditions like diabetes, especially when insulin levels alone might not provide enough information. It can also help determine whether your body is producing enough insulin naturally or if it’s relying on insulin injections or medications.

What does a C-peptide test tell you?

A C-peptide test provides insight into your pancreas’s ability to produce insulin. High levels may suggest overproduction of insulin, while low levels could indicate insufficient insulin production or other pancreatic issues. Unlike insulin, C-peptide is present in the blood regardless of whether insulin is taken by injection or produced naturally.

How is the test performed?

A blood sample is taken from a vein in your arm. The sample is sent to a lab for analysis using a specialized immunoassay method to measure the C-peptide concentration in your serum or plasma.

What might affect results?

Several factors could influence C-peptide levels, including recent meals (especially high-protein foods), certain medications (like insulin or diabetes medications), or conditions affecting blood flow to the pancreas. Stress, illness, or physical activity can also temporarily alter results.