C-peptide (Serum/Plasma) Concentration
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.
["C-peptide helps diagnose diabetes and check insulin production."]
Key facts at a glance
- LOINC
- 56516-8
- Short code
- C peptide 6M p chal SerPl-mCnc
- Synonyms
- C peptide 6M 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?
Doctors may order a C-peptide test to evaluate diabetes diagnosis, monitor insulin production, or assess pancreatic health. It’s often used alongside glucose tests to distinguish between type 1 and type 2 diabetes or to check for insulin resistance.
What to Expect Before the Test
No special preparation is needed. You may have a small needle inserted into a vein (usually in your arm) to draw blood. If fasting isn’t required, you can eat and drink normally. Avoid smoking or caffeine before the test if instructed.
What Happens During the Test
A healthcare provider will clean your arm and insert a needle to collect blood into a tube. The process takes a few minutes. You may feel a brief pinch, but it’s usually over quickly. The blood sample is then sent to a lab for analysis.
What the Results Mean
Results show your C-peptide levels, which can help determine how much insulin your body produces naturally. High levels may indicate type 2 diabetes or insulin resistance, while very low levels could suggest type 1 diabetes or insufficient pancreatic function.
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.
Clinical Significance: C-peptide plays a key role in diabetes management. It helps differentiate between insulin-dependent and insulin-independent diabetes, guides treatment decisions, and assesses long-term pancreatic health. Low or absent C-peptide often signals type 1 diabetes, while elevated levels may indicate overproduction or resistance.
Short name
C-peptide level
Frequently asked questions
How does C-peptide differ from glucose tests?
Can diet or medications affect C-peptide levels?
Is C-peptide testing painful?
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