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C-peptide (Serum/Plasma) Concentration

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

C-peptide is a small protein produced by your pancreas when it releases insulin. This test measures its amount in your blood to help assess insulin production and function.

Quick summary

["This test helps check if your pancreas makes enough insulin naturally."]

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

Key facts at a glance

LOINC
58841-8
Short code
C peptide 5M p chal SerPl-mCnc
Synonyms
C peptide 5M p chal SerPl-mCnc
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
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 evaluate diabetes management, diagnose insulin-dependent conditions, or assess pancreatic health. It can also help distinguish between type 1 and type 2 diabetes by comparing insulin and C-peptide levels.

How Is the Sample Collected?

A blood sample is taken from a vein, usually in your arm. You may feel a small pinch, but it won’t cause significant discomfort. The sample is sent to a lab for analysis.

What Does the Test Result Mean?

Higher-than-normal levels may indicate overproduction of insulin or certain pancreatic disorders. Lower-than-normal levels suggest insufficient insulin production, which could relate to diabetes or other metabolic conditions. Results are interpreted by your healthcare provider based on your overall health and medical history.

Common Reasons for Testing

Doctors often use C-peptide testing to confirm diabetes diagnosis, monitor insulin therapy effectiveness, or investigate unexplained symptoms like fatigue, weight changes, or recurrent infections.

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 tell me about my diabetes?
It helps determine whether your diabetes is insulin-dependent (type 1) or insulin-resistant (type 2). High C-peptide levels may suggest type 2 diabetes, while low levels could indicate type 1 or poor insulin production.
Can food or medications affect my C-peptide test results?
Avoid eating or drinking anything (except water) for 8–12 hours before testing. Some medications (like insulin) may influence results, so discuss this with your doctor.
How often should I get this test?
Your doctor will decide based on your health needs—typically during diabetes management, before insulin therapy, or if symptoms suggest pancreatic issues.
  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