C-peptide (Serum or Plasma)

Why Is This Test Done?

Your doctor may order a C-peptide test to check if your pancreas is making enough insulin. It’s often used to diagnose type 1 diabetes (where the body doesn’t produce insulin) or to evaluate insulin production in people with type 2 diabetes or other conditions affecting insulin. It can also help determine if insulin therapy is needed or if your body is responding well to treatment.

How Is the Sample Collected?

A blood sample is taken from a vein in your arm, usually in a clinic or lab. The blood is collected in a special tube that prevents clotting and separates serum or plasma from cells. You may feel a small pinch when the needle goes in, but it usually doesn’t cause discomfort afterward.

What Does the Test Result Mean?

C-peptide levels can vary based on diet, stress, and other health factors. High levels may indicate your pancreas is producing insulin normally, while low levels could suggest reduced insulin production. Your doctor will interpret the result in relation to your medical history and symptoms.

Common Reasons for Testing

A C-peptide test is often done when diagnosing diabetes, checking for insulin resistance, or evaluating how well insulin therapy is working. It can also help distinguish between type 1 and type 2 diabetes by comparing insulin and C-peptide levels.