C-Peptide

Assesses how much insulin your body makes on its own.

To assess endogenous insulin secretion and glucose metabolism.

1. Check in advance whether the time of day, the day of your menstrual cycle or other timing matters.
2. If the test is ordered to assess insulin production and glucose metabolism, agree on the collection time and fasting in advance. Tell your care team about any diabetes medicines you take.
3. Tell your doctor about hormone preparations and dietary supplements; do not change your treatment on your own.
4. Stay calm before the blood draw and keep to the time agreed with you.

Guidance: often. Check the fasting requirements in advance; if you are asked to fast, drink nothing but water.

A specific time is generally not required. If your doctor has set a different time, follow those instructions.

• Hormone preparations and supplements
• Blood draw time or cycle phase, when relevant
• Immunoassay interference, including biotin on some platforms

Venous blood — serum or plasma, depending on the method

The blood sample is collected by a qualified staff member. The tube type, required volume, and processing and storage conditions are set by the laboratory's specific method. You do not need to store the sample yourself.

C-peptide is a marker of endogenous insulin secretion; the result is interpreted together with the glucose level.

If your result is outside the reference interval, you have symptoms, or your condition changes, contact your doctor. If symptoms are severe or develop quickly, seek emergency care.

Do not stop treatment on your own. Confirm the final test conditions with the laboratory.