C-peptide (Serum/Plasma, Quantitative)
This test measures the amount of C-peptide in your blood. C-peptide is a natural byproduct produced along with insulin during normal insulin production in your pancreas.
["C-peptide helps assess insulin production and diagnose diabetes or pancreatic issues."]
Key facts at a glance
- LOINC
- 57648-8
- Short code
- C peptide 5M pre chal SerPl-sCnc
- Synonyms
- C peptide 5M pre 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 healthcare provider may order a C-peptide test to evaluate your pancreas’s ability to produce insulin. It can help diagnose type 1 or type 2 diabetes, rule out insulin resistance, or check for pancreatic disorders. Some tests may also be used to monitor treatment effectiveness in people with diabetes.
What to Expect Before the Test
No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it’s part of a glucose tolerance or insulin tolerance test. Bring any medications you’re taking to your appointment.
How the Test Is Performed
A blood sample is drawn from a vein (typically in your arm) by a healthcare professional. The sample is sent to a lab for analysis using an immunoassay method to measure C-peptide concentration.
What the Results Mean
Results are interpreted by your healthcare provider based on your medical history and symptoms. High or low levels may indicate different conditions, such as diabetes, insulinoma, or pancreatic disease. Reference ranges vary by lab and may not apply to all individuals.
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 because they reflect endogenous insulin production. In type 1 diabetes, C-peptide levels are often low or absent due to autoimmune destruction of pancreatic beta cells. In type 2 diabetes, C-peptide levels may be normal or slightly reduced, depending on disease progression. Elevated levels could suggest conditions like insulinoma or Cushing’s syndrome. Monitoring C-peptide helps guide treatment decisions, such as insulin therapy or managing pancreatic disorders.
Short name
C-peptide level
Frequently asked questions
What Does a Low C-peptide Level Indicate?
What Does a High C-peptide Level Indicate?
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