Blood Sugar & Metabolism
C-Peptide
Blood Sugar & Metabolism
Measures insulin production by the pancreas. Helps distinguish type 1 from type 2 diabetes.
VAT-exempt medical service
When the pancreas produces insulin, it releases C-peptide in equal measure. C-peptide breaks down more slowly than insulin, so it gives a steadier measure of your own insulin production. The test is used mainly to distinguish type 1 from type 2 diabetes, and to judge how much of your own insulin remains if you are treated with insulin.
Both high and low insulin production matter clinically. High values are common in insulin resistance and early type 2 diabetes, while low values suggest insulin production is failing. The test is relevant at a new diabetes diagnosis, when the type is unclear, and during insulin treatment. It is always interpreted alongside blood glucose or HbA1c from the same occasion.
What a high value can mean
A high C-peptide means the pancreas is producing a lot of insulin. This is usually seen in insulin resistance, where cells respond less well to insulin and the pancreas compensates by producing more. It occurs with excess weight, early type 2 diabetes and metabolic syndrome. Other causes include kidney failure, excess cortisol, pregnancy, certain diabetes medicines and, rarely, an insulin-producing tumour.
What a low value can mean
A low C-peptide means your own insulin production is low. In type 1 diabetes the immune system has attacked the insulin-producing cells, and the value is then very low or undetectable. Low values are also seen in long-standing type 2 diabetes as insulin production declines, in disease of the pancreas, and after prolonged fasting.
The test is usually taken fasting, for at least ten hours. You may drink water. Bring valid ID to your appointment. If you are following the value over time, it helps to use the same laboratory, as methods differ slightly.
Order your test
Choose your test and pay online. Your lab referral is created straight away.
Give your sample
Visit any of our partner sampling locations. No appointment needed at most of them.
The lab analyses it
Your sample is analysed at an accredited Swedish laboratory.
Get your results
Your values appear in your account with reference ranges and an explanation of each marker.
That the pancreas is producing more insulin than normal, usually in response to insulin resistance. It is seen with excess weight, early type 2 diabetes and metabolic syndrome. The value is interpreted alongside blood glucose or HbA1c.
In type 1 diabetes, your own insulin production is severely reduced and C-peptide is very low or undetectable. In type 2 diabetes the value is often normal or high, because insulin is still produced but works less well. The type is determined by a doctor together with other tests, including antibodies.
Yes. An insulin test cannot distinguish injected insulin from insulin your body makes. C-peptide measures only your own production.
Yes. In type 2 diabetes the value is often high early on and falls over the years as insulin production declines. Increased physical activity and weight loss can improve insulin sensitivity and affect the value.