C-peptide (Serum/Plasma, Quantitative)
This test measures the amount of C-peptide, a small protein produced equally with insulin during digestion of food, helping assess how well your pancreas is producing insulin.
["C-peptide helps evaluate insulin production and diagnose diabetes or pancreatic issues."]
Key facts at a glance
- LOINC
- 58513-3
- Short code
- C peptide 4.5h p Glc SerPl-sCnc
- Synonyms
- C peptide 4.5h p Glc SerPl-sCnc
- Category
- glucose
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 0.8
- Ref high
- 1.2
- Critical range
- — – 5 N/A
- Fasting
- true
- 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 Is Done
Your doctor may order a C-peptide test to check if your pancreas is making enough insulin. It can help diagnose type 1 or type 2 diabetes, rule out insulin resistance, or assess how well insulin therapy is working. It’s also used to distinguish between insulin-dependent and non-insulin-dependent diabetes in some cases.
How the Test Works
A blood sample is taken from a vein in your arm. The lab uses a specialized immunoassay (often clia or fia) to measure the tiny amounts of C-peptide in your serum or plasma. This test does not require fasting unless specified by your doctor.
What to Expect Before the Test
No special preparation is needed unless instructed by your healthcare provider. You may have a small needle inserted to draw blood, which can cause a brief sting. If you’re on blood thinners, let your doctor know before the test.
What the Results Mean
Results are compared to a reference range, but exact values can vary by lab. High levels may suggest overproduction of insulin, while low levels could indicate diabetes or pancreatic problems. Your doctor will interpret results in the context of your medical history and symptoms.
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.
◆Associated findings1
Short name
C-peptide level
Frequently asked questions
How often do I need this test?
Can I eat or drink before this test?
What if my results are abnormal?
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