C-Peptide Test
This test measures the level of C-peptide in a sample of your blood or urine (pee).
This test measures the level of C-peptide in a sample of your blood or urine (pee). C-peptide is a chain of amino acids (the building blocks of proteins) that your pancreas makes in the process of making insulin. Insulin is a hormone that your pancreas makes to help blood glucose (blood sugar) get into your cells, where it can be used for energy. This helps keep your blood glucose at healthy levels. C-peptide and insulin enter your bloodstream at the same time and in equal amounts, but C-peptide stays in your blood longer. It is also unaffected by outside sources of insulin such as the medicines involved in diabetes treatment. In other words, C-peptide can give an accurate picture of how much insulin your body is making naturally. Because of this, health care providers may rely on a C-peptide test to measure insulin levels rather than testing insulin levels directly. Other names: insulin C-peptide, connecting peptide insulin, proinsulin C-peptide
Why is this test ordered? You may need a C-peptide test if you have been diagnosed with a pancreatic tumor (insulinoma) or hypoglycemia (low blood glucose) without a clear cause. Hypoglycemia is a condition in which your blood glucose is lower than what is healthy for you. If you have hypoglycemia, you may experience: Shakiness Sweating Headache Hunger or nausea An irregular or fast heartbeat (called arrhythmia ) Dizziness Fatigue In more extreme cases, hypoglycemia can cause confusion, coma , and seizures . You may also need the test if you have diabetes and: Take insulin, and your provider is considering changing your treatment. Have type 2 diabetes, and your provider wants to see if you need to start taking insulin. Have hypoglycemia, which could be caused by taking too much diabetes medicines.
Clinical Interpretation
The meaning of your results depends on your age, health, the medicines you take, and the results of other tests, such as a blood glucose test . In general: A high level of C-peptide usually means that your body is making too much insulin. Conditions that cause insulin levels that are high for you include: Type 2 diabetes. Cushing's syndrome . Insulinoma, a tumor in your pancreas. Kidney failure . A low level of potassium in your blood. A low level of C-peptide may mean your body isn't making enough insulin. Conditions that cause insulin levels that are low for you include: Type 1 diabetes and, in some cases, type 2 diabetes. Taking too much insulin to treat diabetes, which may block your pancreas from making insulin on its own. A severe infection. Addison disease . Liver disease . If you have been treated for an insulin-producing tumor in your pancreas, a decrease in your C-peptide levels means your treatment is working. An increase in your C-peptide may mean that your tumor is back. If you have questions about your results, talk with your provider. Learn more about laboratory tests, reference ranges, and understanding results .
Clinical Protocol & Patient Advice
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For a C-peptide blood test, you may need to fast (not eat or drink) for 8-12 hours before the test. Your provider may also want to test C-peptide after you've eaten something. This way, they can see what your C-peptide levels are when your pancreas is actively working. Ask your provider if there are any specific instructions you need to follow before either a blood or a urine test.
Usage Guidance
- Reference ranges vary by laboratory. Always discuss your specific results with a qualified healthcare professional.
Source: MedlinePlus, National Library of Medicine. View the original.