A C-peptide blood test is a laboratory test that measures the level of C-peptide in the blood. C-peptide is a byproduct of insulin production in the body, and is released in equal amounts to insulin during insulin synthesis. Insulin is a hormone produced by the pancreas that helps regulate blood sugar levels.

The C-peptide blood test may be used to diagnose and monitor diabetes, particularly type 1 diabetes, as well as to distinguish between type 1 and type 2 diabetes. In type 1 diabetes, the body’s immune system attacks and destroys the cells in the pancreas that produce insulin, leading to a decrease in insulin production and an increase in blood sugar levels. In type 2 diabetes, the body becomes resistant to insulin and/or the pancreas gradually produces less insulin over time.

During the test, a healthcare professional will draw a blood sample from your arm and send it to a laboratory for analysis. The results of the test are reported as the amount of C-peptide present in your blood, usually measured in nanograms per milliliter (ng/mL) or picomoles per liter (pmol/L).

Normal levels of C-peptide in the blood vary depending on factors such as age and weight, but generally range from 0.5 to 4.0 ng/mL or 0.17 to 1.32 pmol/L. Higher levels may indicate that the pancreas is still producing insulin, while lower levels may indicate a decrease in insulin production.

If your C-peptide levels are low, your healthcare provider may recommend additional tests to confirm the diagnosis of diabetes and determine the appropriate treatment. Treatment for type 1 diabetes may include insulin therapy, while treatment for type 2 diabetes may include lifestyle changes such as diet and exercise, oral medications, and/or insulin therapy.

Overall, the C-peptide blood test is a useful tool for assessing insulin production and diagnosing and monitoring diabetes. If you have concerns about your blood sugar levels or have been diagnosed with diabetes, it is important to talk to your healthcare provider about whether a C-peptide blood test or other tests may be appropriate for you.