Updated: September 29, 2019
The connecting peptide or C-peptide test is done to monitor and treat diabetes. It shows how well your body makes insulin, which moves sugar or glucose from your blood into your cells. C-peptide is a byproduct created when insulin is produced. Measuring the amount of C-peptide in blood indicates how much insulin is being produced.
Insulin is the hormone that is responsible for lowering blood glucose levels which is produced by beta cells in the pancreas. Our body will break down the food we eat into glucose and other nutrients, which is then absorbed from the blood by beta cells.
The test can help your doctor decide whether you need to take insulin to control your condition if enough of insulin is not produced by the pancreas or to check your dosage if you already take it. Both Type 1 diabetes, when the immune system attacks and destroys cells in the pancreas, and type 2 diabetes, when your body doesn't produce or use insulin properly can be diagnose by this test.
The insulin C-peptide test is used to monitor insulin production in the body. It can be used to:
This test is also done if you experience the symptoms of hypoglycemia, even if you don't have type 1 or type 2 diabetes. . In this case, the body may be producing too much insulin. Symptoms of hypoglycemia include:
Fasting for 10 to 12 hours before the test is required. During this period you should not eat or drink anything except water. You may also need to stop taking certain medications which can be advised by your doctor.
A band will be tied by a technician around your arm so that the veins of the hand are more prominent to prick the injection. The vein is punctured with a fresh, disposable syringe and the blood is withdrawn after the site is cleaned with an alcohol swab. A cotton swab will be given to you after drawing the blood to place on the place where the injection was pricked. You will be asked to apply pressure on the cotton in order to stop the bleeding. You might notice a bruise in the place where the injection was pricked on your skin. This is normal and should fade away in a few days.
Before you undergo this test, you should inform the the lab technician if you suffer from a bleeding or clotting disorder or are taking medicines like aspirin, warfarin or other blood-thinning agents, as in such cases the bleeding might take a while to stop.
A normal C-peptide range is 0.5 to 2.0 ng/mL (nanograms per milliliter).
An high level may also be due to taking too much of a certain medication to treat type 2 diabetes.