C-peptide (Serum or Plasma, Quantitative)
This test measures the amount of C-peptide in your blood. C-peptide is a small protein released by your pancreas along with insulin during digestion. It helps doctors assess how well your pancreas is producing insulin and whether insulin therapy is working properly.
["C-peptide helps track natural insulin production and insulin replacement effectiveness."]
Key facts at a glance
- LOINC
- 57646-2
- Short code
- C peptide 190M p chal SerPl-sCnc
- Synonyms
- C peptide 190M 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 diabetes management, diagnose type 1 or type 2 diabetes, or check if insulin therapy is working as intended. It can also help distinguish between insulin-dependent and insulin-independent causes of low blood sugar.
What Does the Test Tell You?
High levels may indicate overproduction of insulin (e.g., from a tumor or excessive insulin therapy). Low levels suggest insufficient insulin production, which could be due to diabetes or other pancreatic conditions.
Sample Collection and Preparation
This test requires a blood sample drawn from a vein in your arm. The sample is collected in a tube containing an anticoagulant to prevent clotting. The blood is then sent to a lab for analysis.
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 doctor. Wear comfortable clothing and bring any medications you’re currently taking.
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.
C-peptide levels are critical for diagnosing diabetes, assessing insulin deficiency, and monitoring insulin therapy. In type 1 diabetes, low C-peptide levels confirm the pancreas no longer produces insulin. In type 2 diabetes, elevated C-peptide may indicate residual insulin production despite poor glucose control.
Short name
C-Peptide Level
Frequently asked questions
What causes abnormal C-peptide results?
How long does it take to get results?
Can I eat or drink before 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