C-peptide (Serum/Plasma) Concentration
This test measures the amount of C-peptide, a small protein produced equally with insulin during pancreatic beta-cell activity. It helps assess insulin production and diagnose conditions like diabetes.
["C-peptide helps evaluate your pancreas’s insulin-making ability and supports diabetes management."]
Key facts at a glance
- LOINC
- 38422-2
- Short code
- C peptide 1h p chal SerPl-sCnc
- Synonyms
- C peptide 1h 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 This Test Matters
C-peptide is a natural byproduct of insulin production. Unlike insulin, which circulates briefly and is broken down quickly, C-peptide remains in your bloodstream for longer. This test helps doctors determine how well your pancreas is producing insulin, which is important for diagnosing and managing diabetes and other endocrine disorders.
How It’s Used in Diagnosis
A C-peptide test is often used to distinguish between type 1 and type 2 diabetes. In type 1 diabetes, the pancreas produces little to no insulin, so C-peptide levels are low. In type 2 diabetes, the pancreas may still produce some insulin, so C-peptide levels can be higher. It’s also used to monitor insulin therapy in people with diabetes.
Sample and Testing Process
A blood sample is drawn from a vein, usually in your arm. The blood is then separated to obtain serum or plasma for testing. The test measures the concentration of C-peptide using a sensitive laboratory method, often an immunoassay.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if instructed by your healthcare provider. Wear comfortable clothing and plan to have someone drive you home if you’re taking medications that cause drowsiness.
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
Short name
C-peptide level
Frequently asked questions
How can C-peptide levels help my healthcare provider?
What do abnormal C-peptide results mean?
Can C-peptide test results change over time?
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