C-peptide (Serum or Plasma) with 15-minute postprandial measurement
This test measures C-peptide, a small protein produced equally by your pancreas when insulin is made. It helps assess how well your pancreas is producing insulin naturally.
["C-peptide helps diagnose and monitor diabetes and pancreatic function."]
Key facts at a glance
- LOINC
- 13860-2
- Short code
- C peptide 15M p 1 mg Gc PO SerPl-mCnc
- Synonyms
- C peptide 15M p 1 mg Gc PO 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 healthcare provider may order this test to check if your pancreas is making enough insulin on its own, especially if you have diabetes or symptoms like unexplained weight loss, fatigue, or frequent infections. The postprandial (after-meal) sample helps evaluate how your body responds to food.
What Does It Measure?
C-peptide is a byproduct of insulin production. Unlike insulin, which is cleared quickly from your blood, C-peptide stays in your system for longer. Measuring it helps distinguish between insulin-dependent and insulin-independent sources of glucose regulation.
How Is It Done?
A blood sample is taken from a vein, usually in your arm. The test checks your serum or plasma levels at a specific time (15 minutes after eating). This timing helps assess how your body processes food-related glucose spikes.
What Are Common Uses?
This test is often used to confirm diabetes diagnosis, especially in cases where insulin resistance or other conditions might be suspected. It can also help monitor pancreatic health in people with chronic pancreatitis or other pancreatic disorders.
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 levels can indicate whether your body relies on its own insulin production or requires external insulin. Low levels may suggest insufficient pancreatic function, while normal or high levels can help rule out insulin dependence or overproduction.
Short name
C-peptide (Post-Meal)
Frequently asked questions
What does a postprandial C-peptide test tell me about my diabetes management?
How does this test differ from a fasting C-peptide test?
Can I eat or drink anything before 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