C-peptide (Serum/Plasma, Quantitative)
This test measures the amount of C-peptide, a small protein produced naturally in your body when insulin is made. It helps assess how well your pancreas is producing insulin.
["C-peptide helps evaluate insulin production and diabetes management."]
Key facts at a glance
- LOINC
- 13040-1
- Short code
- C peptide 1.5h p chal SerPl-mCnc
- Synonyms
- C peptide 1.5h p chal 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
What Is C-Peptide?
C-peptide is a byproduct of insulin production. When your pancreas makes insulin, it also releases C-peptide. Unlike insulin, C-peptide stays in your bloodstream longer and can be measured directly. This test is often used to check if your body is producing insulin naturally, which is important for diagnosing and managing diabetes.
Why Might You Need This Test?
Your doctor may order a C-peptide test if you have symptoms of diabetes, such as excessive thirst, frequent urination, or unexplained weight loss. It can also help determine if you have type 1 or type 2 diabetes, or if you’re taking insulin injections but still need natural insulin production.
How Is the Test Done?
A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab for analysis. No special preparation is needed, but you may be asked to fast for a few hours before the test if instructed by your doctor.
What Do the Results Mean?
High levels of C-peptide may suggest your body is producing insulin naturally, even if you have diabetes. Low levels could indicate your pancreas isn’t making enough insulin. Your doctor will interpret the results in the context of your symptoms and other tests.
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 testing plays a key role in distinguishing between insulin-dependent and insulin-independent diabetes, assessing insulin deficiency, and monitoring treatment effectiveness in patients on insulin therapy.
Short name
C-peptide level
Frequently asked questions
Why is C-peptide important for diabetes management?
Can C-peptide test results change over time?
Is fasting required for 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