C-Peptide Serum Test

The C-Peptide Serum Test is useful for monitoring insulin production and diagnosing the cause of hypoglycemia (low blood sugar). The test measures the amount of C-Peptide in the blood.

C-Peptide, also known as connecting peptide, is a short chain of amino acids produced when proinsulin, the precursor to insulin formed in the beta cells of the pancreas, splits into two molecules. When insulin is released into the bloodstream, an equal amount of C-Peptide is also released. As a result, C-Peptide levels are a useful indicator of insulin production.

In patients recently diagnosed with diabetes, C-Peptide levels may be measured to evaluate how much insulin the individual’s pancreas is still able to produce. Levels may be monitored over time to help determine when insulin therapy should begin. Insulin-dependent diabetics may develop antibodies to insulin that interfere with insulin tests, making C-Peptide levels a more accurate reflection of endogenous insulin production (produced by the body).

The C-Peptide Serum Test may also be used to help determine the cause of documented hypoglycemia, such as excess insulin supplementation, hereditary liver enzyme deficiency, liver or kidney disease, or insulinoma (tumor of the islet cells in the pancreas). In patients with an insulinoma, the test may be used to monitor the effectiveness of treatment and detect recurrence.