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C-peptide (Serum) after a Standard Meal

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

This test measures the amount of C-peptide in your blood after eating a standard meal. C-peptide is a substance produced by your pancreas along with insulin.

Quick summary

["Assessing how your pancreas releases insulin after eating."]

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

Key facts at a glance

LOINC
95090-7
Short code
C peptide 5h p meal SerPl-mCnc
Synonyms
C peptide 5h p meal 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

Doctors may order this test to evaluate how well your pancreas produces insulin naturally, especially if you have diabetes or suspect a condition affecting insulin secretion. It helps determine if your body’s insulin production is functioning as expected after eating.

What to Expect Before the Test

You’ll fast for about 8–12 hours before the test, then eat a specific meal provided by the lab. Blood will be drawn shortly after to check your C-peptide levels.

How the Test Works

A sample of your blood is taken and analyzed to measure C-peptide levels. This helps assess your pancreas’s ability to release insulin in response to food.

What the Results Mean

Higher-than-normal levels may indicate your pancreas is producing too much insulin, while lower-than-normal levels could suggest impaired insulin release. Results help guide treatment plans for diabetes or related conditions.

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 or type 2 diabetes, by assessing endogenous insulin production. It can also help distinguish between insulin-dependent and insulin-independent conditions, such as insulinoma or other pancreatic disorders.

Short name

C-peptide post-meal

Frequently asked questions

What does a high C-peptide level mean?
A high level may suggest your pancreas is producing insulin independently of food intake, which could indicate conditions like insulinoma or other hyperinsulinemic disorders.
Why would my doctor order this test?
Your doctor may recommend it to check how well your pancreas produces insulin naturally, especially if you have diabetes symptoms, unexplained weight changes, or other signs of pancreatic issues.
Can I eat before the test?
No, you must fast for 8–12 hours before the test and follow the meal provided by the lab to get accurate results.
  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