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C-peptide (Serum) with 15-Minute Postprandial Collection

Published: August 9, 2026Updated: August 16, 2026

This test measures C-peptide, a small protein produced equally with insulin during digestion. The sample is taken 15 minutes after eating to assess how your pancreas responds to food.

Quick summary

["Helps evaluate how well your pancreas produces insulin after meals."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
38249-9
Short code
C peptide 15M p chal SerPl-mCnc
Synonyms
C peptide 15M 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

Why This Test Is Done

Your doctor may order this test if you have diabetes, suspected diabetes, or symptoms like unexplained weight loss, fatigue, or frequent infections. It helps check if your pancreas is making enough insulin naturally, especially after eating.

What to Expect Before the Test

No special preparation is needed. You’ll eat a meal or snack, then fast for 15 minutes before the blood is drawn. The test may be done during a routine doctor’s visit or at a lab.

How the Test Works

Blood is drawn from a vein, usually in your arm. C-peptide is measured in your serum to see how your body’s natural insulin production responds to food.

What the Results Mean

Results help determine if your pancreas is functioning properly after meals. Low or normal levels may indicate healthy insulin production, while abnormal results could signal issues like diabetes or pancreatic problems.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: serum

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: This test is critical for diagnosing and managing diabetes, particularly Type 1 diabetes, where the pancreas doesn’t produce insulin. It also helps monitor how well insulin production responds to dietary changes or medical treatments.

Short name

C-peptide (15 min post-meal)

Frequently asked questions

How long does it take to get results from this test?
Results are typically available within 1–3 business days, depending on your lab’s processing time.
Can I eat before the test?
Yes, eat a normal meal or snack, then fast for 15 minutes before the blood is drawn. Avoid skipping meals unless instructed otherwise.
Is there any risk or discomfort with this test?
There’s minimal discomfort from the needle stick, which usually takes only a few seconds. Most people feel minor bruising or soreness afterward, which goes away quickly.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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