This test measures the level of C-peptide in a sample of your blood or urine (pee). Measuring C-peptide is an accurate way to find out how much insulin your body is making.

Insulin is a hormone that your pancreas makes. It helps blood glucose (blood sugar) get into your cells, where it can be used for energy. This helps keep your blood glucose at healthy levels.

During the process of making insulin, your pancreas produces C-peptide. C-peptide and insulin enter your bloodstream at the same time and in equal amounts. C-peptide doesn't affect your blood glucose levels, but it stays in your blood longer than insulin, so it's easier to measure accurately.

A C-peptide test can provide important information to help understand, monitor, and/or treat disorders that involve how well your body makes insulin, such as hypoglycemia (low blood sugar) and diabetes.