C-peptide (Serum/Plasma, Mass Concentration)
This test measures the amount of C-peptide, a small protein produced along with insulin when your pancreas releases it to regulate blood sugar. It helps assess how well your pancreas is producing insulin naturally.
C-peptide helps evaluate your body’s insulin production and function.
Key facts at a glance
- LOINC
- 13859-4
- Short code
- C peptide 10M p 1 mg Gc IV SerPl-mCnc
- Synonyms
- C peptide 10M p 1 mg Gc IV SerPl-mCnc
- 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 check if your pancreas is making enough insulin. It can also help diagnose conditions like diabetes, determine if you have insulin-producing tumors, or monitor how well insulin therapy is working. Sometimes, it’s used alongside other tests to understand how your body responds to glucose.
What Does the Test Involve?
A blood sample is taken from a vein in your arm. The sample is sent to a lab where it’s analyzed to measure C-peptide levels. No special preparation is usually needed, but you may be asked to fast for a few hours before the test if instructed by your doctor.
What Are the Results Typically Used For?
High C-peptide levels may suggest your body produces insulin naturally, while low levels could indicate problems like diabetes or insufficient insulin production. Your doctor will interpret the results in the context of your medical history and other tests.
What Might Affect My Results?
Several factors can influence C-peptide levels, including recent meals (especially high-carb foods), stress, illness, or certain medications that affect blood sugar. If you’re on insulin or diabetes medications, your doctor may adjust your test timing to get the most accurate results.
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 is a reliable marker for endogenous insulin production. Unlike insulin, which can be artificially added (e.g., from injections), C-peptide is naturally produced by the pancreas. High levels often mean your body makes insulin independently, while low levels may signal diabetes, pancreatic insufficiency, or other metabolic disorders. It’s particularly useful in distinguishing between type 1 and type 2 diabetes or evaluating insulinomas (rare tumors that produce excess insulin).
Short name
C-peptide level
Frequently asked questions
How long does it take to get my C-peptide test results?
Can I eat or drink before this test?
Is there any risk or discomfort with this blood 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