C-peptide (High-Performance Liquid Chromatography, Serum/Plasma)
This test measures the amount of C-peptide, a byproduct of insulin production, in your blood. It helps assess how well your pancreas is making insulin.
["C-peptide helps evaluate insulin production and diabetes management."]
Key facts at a glance
- LOINC
- 58494-6
- Short code
- C peptide 1.5h p Glc SerPl-mCnc
- Synonyms
- C peptide 1.5h p Glc SerPl-mCnc
- 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 Is This Test Done?
Doctors may order a C-peptide test to diagnose or monitor diabetes, especially when insulin levels alone aren’t sufficient. It can also help distinguish between types of diabetes or rule out conditions like insulinoma (a rare tumor that causes excessive insulin production).
What Does the Result Mean?
Your result reflects how much insulin your pancreas naturally produces. Low levels may suggest diabetes or insufficient insulin secretion, while normal or high levels can help confirm healthy insulin function or rule out overproduction of insulin.
How Is the Test Performed?
A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab for high-performance liquid chromatography (HPLC) to measure C-peptide concentration.
What Should You Know Before the Test?
No special preparation is needed, but inform your doctor about any medications (especially insulin or diabetes drugs) or recent illnesses that might affect results. Avoid fasting unless instructed, as it may impact interpretation.
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 is a key marker for insulin physiology. It helps differentiate between type 1 diabetes (where the pancreas produces little to no insulin) and type 2 diabetes (where insulin production may be impaired but not zero). It’s also used to monitor insulinoma or evaluate pancreatic function in non-diabetic conditions.
Short name
C-peptide level
Frequently asked questions
What causes abnormal C-peptide levels?
Does diet or fasting affect C-peptide results?
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