Test library
Serum C-Peptide Test
The C-Peptide blood test measures C-peptide, a byproduct of insulin production, to help assess how much insulin the pancreas is making. It is used in the evaluation of diabetes, hypoglycemia, and insulin-related conditions.
Order C-Peptide, Blood Test
Order online and visit a local collection site, or choose an at-home kit where available. No referral and no insurance required.
Order C-Peptide, Blood Test- Typical turnaround
- 1-3 business days
- Starting price
- From $198
- Results
- Confidential, online
Quick answer
The C-Peptide blood test measures C-peptide, a substance released when the pancreas produces insulin. Because C-peptide and insulin are made together, the level offers a window into how much insulin the body is producing on its own. It is commonly used to evaluate diabetes, episodes of low blood sugar, and some insulin-related conditions.
What this test measures
C-peptide is a small protein that is split from proinsulin when the pancreas makes insulin. For every molecule of insulin released, a molecule of C-peptide is released as well. Measuring C-peptide therefore provides an indirect but reliable estimate of the body's own insulin production, separate from insulin that may have been injected as medication.
The test uses a blood sample, usually drawn from a vein at the arm. In some cases it is collected alongside a glucose measurement or during a fasting evaluation. Results are reported as a concentration, and clinicians often compare the C-peptide level with the glucose level to interpret the relationship between insulin production and blood sugar.
Clinicians may order C-peptide to help distinguish between types of diabetes, to investigate hypoglycemia, or to check whether the pancreas is still producing insulin. It can also be used to evaluate a suspected insulinoma or to monitor a known condition. The result is interpreted with other tests and clinical findings, not on its own.
- C-peptide
- Insulin
- Glucose
- Proinsulin
- Hemoglobin A1c when included
- Insulin antibodies when included
- Beta-hydroxybutyrate when included
Why people order this test
- Distinguish type 1 from type 2 diabetes
- Evaluate the cause of low blood sugar (hypoglycemia)
- Assess remaining pancreatic insulin production
- Investigate a suspected insulinoma
- Monitor a known diabetes or pancreatic condition
- Support decisions about insulin treatment with a provider
How to prepare
Fasting is often requested for a C-peptide test, and some orders specify a sample collected after an overnight fast. The laboratory may also coordinate the draw with a glucose measurement. Follow the exact timing and fasting instructions provided with the order.
Understanding your results
Results are usually available within one to three business days. A low level suggests reduced insulin production, while a high level suggests increased production. Because the meaning depends on the glucose level at the same time, a qualified healthcare provider interprets the result in context.
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Frequently Asked Questions
What is C-peptide?
C-peptide is a byproduct released when the pancreas produces insulin. Its level reflects how much insulin the body is making on its own.
Why measure C-peptide instead of insulin?
C-peptide stays in the bloodstream longer than insulin and is not present in injected insulin preparations, which makes it a useful marker of the body's own insulin output.
Do I need to fast?
Fasting is commonly requested for C-peptide testing. Some orders also pair it with a glucose measurement. Follow the instructions supplied with your order.
Does a low C-peptide mean I need treatment?
A low result can indicate reduced insulin production, but it does not by itself determine treatment. A qualified healthcare provider makes that assessment with other information.
Can the test detect an insulinoma?
It can contribute to the evaluation of a suspected insulinoma, usually alongside glucose and other tests. A single result is not a diagnosis.
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Order online and visit a collection site near you, or choose a mail-in kit. No referral and no insurance required.
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