C-peptide (Serum/Plasma)
This test measures the amount of C-peptide, a small protein produced naturally by your pancreas along with insulin when your body converts food into energy.
["C-peptide helps assess insulin production and diagnose diabetes or pancreatic issues."]
Key facts at a glance
- LOINC
- 77651-8
- Short code
- C peptide 75M p chal SerPl-sCnc
- Synonyms
- C peptide 75M p chal SerPl-sCnc
- 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 how well your pancreas is producing insulin, check for diabetes, or monitor conditions like insulinoma (a rare tumor affecting insulin production). It can also help distinguish between types of diabetes or rule out other causes of low insulin levels.
What Does the Test Involve?
A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab for analysis using an immunoassay method to measure C-peptide concentration.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if instructed by your healthcare provider.
What to Expect After the Test
You’ll typically feel normal after the blood draw. Apply pressure to the site to stop any bleeding, and avoid heavy lifting for a few hours. Check with your doctor if you experience unusual pain or swelling.
Reference range
INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A
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.
A C-peptide test is crucial for diagnosing diabetes (especially Type 1), assessing insulin-dependent conditions, and confirming whether insulin is being produced naturally. High levels may indicate normal insulin production, while low levels can signal diabetes or other pancreatic disorders. It helps differentiate between insulin-dependent and insulin-independent diabetes and can guide treatment decisions.
Short name
C-peptide level
Frequently asked questions
What does a high or low C-peptide level mean?
How long does it take to get results?
Can fasting affect C-peptide test results?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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