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C-peptide (Serum/Plasma)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of C-peptide, a natural byproduct of insulin production, in your blood. It helps assess how well your pancreas is making insulin.

Quick summary

["C-peptide helps evaluate insulin production and diabetes management."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
47595-4
Short code
C peptide pre Glc SerPl-sCnc
Synonyms
C peptide pre Glc SerPl-sCnc
Category
glucose
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
true
Population
adult
Sex
all
Age range
18–65 years
CPT
85610
SNOMED
396252006
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order a C-peptide test to check if your pancreas is producing enough insulin. It can also help diagnose or monitor conditions like type 1 or type 2 diabetes, insulinoma (a rare tumor that causes high insulin levels), or to assess how well insulin therapy is working. Sometimes, it’s used alongside glucose tests to better understand insulin function.

How Is the Sample Collected?

A blood sample is taken from a vein, usually in your arm. You may feel a small pinch when the needle goes in, but it usually stops quickly. The blood is sent to a lab for testing.

What Does the Result Mean?

Results don’t come with a standard range because they vary by lab and health status. Higher levels may suggest overproduction of insulin (e.g., insulinoma), while lower levels could indicate poor insulin production (e.g., type 1 diabetes). Your doctor will interpret results in relation to your overall health and symptoms.

Common Reasons for Testing

Doctors may recommend this test if you have symptoms of diabetes, unexplained low blood sugar, or if you’re being evaluated for insulin-related conditions. It can also help monitor how well diabetes treatments are working.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: serum

Inform your healthcare provider if you are taking blood thinners. No special preparation required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

C-peptide level

Frequently asked questions

What does a C-peptide test measure?
It measures the amount of C-peptide, a protein released with insulin from your pancreas. This helps doctors check how well your pancreas is producing insulin naturally.
How long does it take to get results?
Results are typically available within a few days to a week, depending on your lab’s processing time. Your doctor will contact you once they’re ready.
Can I eat or drink before this test?
For most C-peptide tests, fasting isn’t required, but follow your doctor’s instructions. If you’re unsure, ask before your appointment.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy