What is C-peptide?
This test measures the amount of C-peptide in the blood. C-peptide and insulin are produced in the pancreas at the same rate and released into the bloodstream in equal amounts when insulin is required in response to increased glucose levels. C-peptide stays in the bloodstream longer than insulin, making it a useful marker of insulin production. It can be used to differentiate between Type I and Type II diabetes.
Low or no C-peptide means that your pancreas produces little or no insulin. This could be normal if you have not eaten recently, as your blood sugar and insulin levels are naturally low when fasting.
Why test C-peptide?
What causes low C-peptide levels?
Low C-peptide levels suggest that your pancreas isn’t working well, and your body isn’t making enough insulin. Possible reasons include diabetes Type I and Type II, insulin therapy, low blood glucose in diabetics on insulin, long periods of fasting or starvation, and poor pancreas function from, for example, pancreatitis.
Symptoms of low C-peptide
Low C-peptide levels indicate reduced insulin production, often linked to type 1 diabetes or advanced type 2 diabetes. Symptoms include frequent urination and increased thirst as the body tries to eliminate excess glucose, unintended weight loss as fat and muscle are used for energy, and constant fatigue because glucose can't enter cells. You might also experience blurred vision from eye swelling and slow healing of cuts and bruises due to high glucose levels. If you notice these symptoms, it's important to consult a doctor for evaluation and treatment.
What causes high C-peptide levels?
A high level of C-peptide usually indicates a high level of insulin production. This can be in response to a high blood glucose caused by glucose intake, insulin resistance, or both. Higher than expected C-peptide levels can be caused by eating a high-carbohydrate meal, insulin resistance, obesity, kidney disease, cortisol excess due to Cushing syndrome and occasionally insulin-producing benign tumours. Some medications increase C-peptide, including diabetes medications and glucocorticoids. Pregnancy can increase C-peptide levels.
Symptoms of high C-peptide
High C-peptide levels can indicate excessive insulin production, often associated with conditions like type 2 diabetes, insulin resistance, or a pancreatic tumour. Symptoms of high C-peptide levels include frequent hunger, weight gain, and difficulty losing weight due to the body's inability to use insulin effectively. You might also experience fatigue and low energy levels as the body struggles to manage blood sugar properly. Additionally, high C-peptide levels can cause increased thirst and frequent urination as the body attempts to eliminate excess glucose. If you notice these symptoms, it is important to consult a doctor for proper evaluation and treatment.
More information
Repeat C-peptide tests should be undertaken by the same laboratory using the same method. For instance, if you have previously had a test done at Karolinska you should repeat the test at Karolinska.
Preparations for this test
Do not eat or drink anything except water for at least 10 (preferably 12) hours before taking this test.
On the day
Always take I.D. with you when going to take a test. Arrive early and sit down quietly for 15 minutes before taking a test.