Other names: Insulin C-Peptide

This test measures the levels of C-peptide in the blood; a urine test may also be carried out to measure C-peptide levels. C-peptide is released into the bloodstream at the same time as insulin; this means that measuring the amount of C-peptide in the blood can also determine insulin levels. The test can also be used to measure the amount of endogenous insulin being produced by the body; endogenous insulin is produced by the body’s beta cells in contrast to exogenous insulin, which is put into the body, usually by means of an insulin injection.

Why is the test used?

The C-peptide test is used to measure the levels of C-peptide in the blood; it is also used to help doctors assess the production of endogenous insulin. The test is usually ordered for patients with hypoglycaemia (also known as low blood sugar); symptoms of hypoglycaemia include dizziness, sweating, palpitations, hunger and seizures. The test is usually used for patients with type 1 or type 2 diabetes; the test helps to assess the production of insulin in the body and the results can be used to determine a suitable treatment pathway.

How is the test carried out?

The test is done by taking a sample of blood from a vein in the arm; a needle is inserted into the vein and the blood is collected in a syringe. Once the sample has been collected, it can then be bottled, labelled (with the patient’s name) and sent away for analysis.

What do the test results mean?

High levels of C-peptide usually indicate that the body is producing a large amount of insulin. High levels of C-peptide may be caused by excessive production of insulin by the body, insulin resistance (when the body does not respond well to insulin) or as a response to high levels of glucose in the blood. High levels of C-peptide may also be associated with pregnancy, Cushing’s syndrome and kidney disease.

Low levels of C-peptide mean that the body is not producing as much insulin as it should be. Low levels may also be associated with drinking alcohol on a regular basis and taking certain types of medication, including diuretics.

Specific Blood Tests

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