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C-peptide measured after a standardized high-protein meal via plasma concentration

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

This test evaluates how your pancreas produces insulin after eating a meal high in protein. It helps assess your body’s ability to manage blood sugar naturally.

Quick summary

["Measures natural insulin production response to food."]

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

Key facts at a glance

LOINC
95083-2
Short code
C peptide 2.5h p meal SerPl-mCnc
Synonyms
C peptide 2.5h 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

Your doctor may order this test if you have diabetes, prediabetes, or suspected insulin resistance. It can also help diagnose conditions like pancreatic disease or check how well your pancreas is functioning after surgery or treatment.

What to Expect Before the Test

You’ll follow a specific meal plan (high-protein) the day before your test. Blood will be drawn after the meal to measure C-peptide levels in your plasma. No special preparation is needed beyond this.

How the Test Works

C-peptide is a byproduct of insulin production. By measuring it, doctors can determine how much insulin your pancreas releases naturally, independent of insulin levels alone.

What the Results Mean

Results help assess insulin secretion and rule out issues like insulinoma (tumor causing excess insulin) or pancreatic damage. Lower-than-expected levels may indicate poor pancreatic function.

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 insulin-related disorders, monitoring diabetes management, and evaluating pancreatic health. It provides insight beyond standard glucose tests alone.

Short name

C-peptide post-meal plasma

Frequently asked questions

What does a high C-peptide level mean?
A high level suggests your pancreas is producing insulin naturally, which may indicate diabetes or insulin resistance. It can also help distinguish between diabetes caused by insulin-producing tumors and other types.
How long does it take to get results?
Results are typically available within 1–3 business days after your lab receives the sample.
Can I eat or drink anything before the test?
No—you must follow the high-protein meal plan provided by your doctor the day before testing. Avoid alcohol or sugary foods/snacks unless instructed otherwise.
  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