C-peptide (Serum or Plasma, Quantitative)
This test measures the amount of C-peptide, a small protein produced equally with insulin during digestion of food. It helps assess how much insulin your pancreas naturally makes.
["C-peptide helps diagnose and monitor diabetes and pancreatic function."]
Key facts at a glance
- LOINC
- 58515-8
- Short code
- C peptide 45M p Glc SerPl-sCnc
- Synonyms
- C peptide 45M 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 produces insulin normally. It’s often used to diagnose type 1 diabetes, type 2 diabetes, or to evaluate insulin resistance. It can also help determine if insulin injections are working properly in people with diabetes.
How the Test Works
A blood sample is taken from a vein in your arm. The lab measures the concentration 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, but you may be asked to stop certain medications or avoid foods that could affect results. Always follow your doctor’s instructions.
What the Results Mean
High levels of C-peptide may indicate your pancreas is producing insulin despite diabetes. Low levels suggest poor insulin production or possible pancreatic issues. 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.
C-peptide levels are critical for diagnosing diabetes subtypes, assessing insulin dependency, and monitoring pancreatic health. It can also help differentiate between insulin-producing tumors and other conditions affecting insulin metabolism.
Short name
C-peptide level
Frequently asked questions
What causes abnormal C-peptide levels?
How long does it take to get results?
Can diet or medications affect C-peptide test results?
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