C-peptide (Serum or Plasma) Concentration
This test measures the amount of C-peptide, a natural substance produced by your pancreas along with insulin during blood sugar regulation. It helps assess how well your pancreas is producing insulin.
["C-peptide helps doctors check insulin production and diagnose diabetes or other pancreatic conditions."]
Key facts at a glance
- LOINC
- 58499-5
- Short code
- C peptide 15M p 1 mg Gc PO SerPl-sCnc
- Synonyms
- C peptide 15M p 1 mg Gc PO 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 this test to evaluate your pancreas’s ability to produce insulin, diagnose or monitor diabetes, or check for conditions like insulinoma (a rare tumor that causes excessive insulin production). It’s also used to distinguish between insulin-dependent and insulin-independent diabetes.
What Does a Low or High Level Indicate?
Low levels may suggest your pancreas isn’t producing enough insulin, while high levels could indicate overproduction (e.g., from an insulin-secreting tumor). Normal levels help confirm diabetes or rule out other causes of blood sugar issues.
How Is the Test Performed?
A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab to measure C-peptide concentration using an immunoassay method, which detects the protein without relying on insulin levels alone.
What Should You Expect Before the Test?
No special preparation is needed, but avoid eating or drinking for at least 8–12 hours before the test if instructed by your doctor. Wear comfortable clothing and inform staff about any allergies or conditions.
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 is critical for diagnosing and managing diabetes and pancreatic disorders. It provides insight into endogenous insulin production, helping differentiate between types of diabetes or rule out functional insulinomas. Monitoring C-peptide levels can also guide treatment decisions, such as insulin therapy adjustments.
Short name
C-peptide level
Frequently asked questions
What does a C-peptide test tell me about my diabetes?
Can food or medications affect my C-peptide test results?
How often should I get this test?
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