C-peptide

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.

Why Test C-Peptide?

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 Do High C-Peptide Levels 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 Do Low C-Peptide Levels 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.

Symptoms to Watch For

Increased thirst and passing large amounts of urine
Unintended weight loss
Persistent fatigue and lack of energy
Blurred vision
Wounds that heal slowly
Strong hunger or difficulty feeling full
Tingling or numbness in hands and feet

Who Should Get Tested?

People recently diagnosed with diabetes where the type is unclear
People treated with insulin who want to know how much of their own insulin remains
People with diabetes or insulin resistance in the family
People with symptoms of disturbed blood glucose
People being investigated for repeated episodes of low blood glucose

How to Prepare for Your Test

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.

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Test your C-Peptide levels with an accredited Swedish laboratory. Results within days, reviewed by Wellth.

C-Peptide →

Frequently Asked Questions

What does a high C-peptide mean?

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.

How does C-peptide distinguish type 1 from type 2 diabetes?

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.

Is the test useful if I take insulin?

Yes. An insulin test cannot distinguish injected insulin from insulin your body makes. C-peptide measures only your own production.

Can C-peptide change over time?

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.

Reviewed by

Wellth Team

Wellth

Our content is written and reviewed by Wellth, and fact-checked against peer-reviewed research and current Swedish clinical guidelines.

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Medical Disclaimer

The information on this page is provided for informational purposes only and does not constitute professional medical advice, diagnosis, or treatment. Wellth provides health information and testing services but is not a substitute for clinical care. Always consult a qualified healthcare provider if you have questions about a medical condition. If you are experiencing severe or urgent symptoms, contact your doctor or call 1177 Vårdguiden. Blood test results should be interpreted by a qualified healthcare professional in the context of your complete medical history.