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C-peptide (Serum) with High-Protein Meal Stimulation

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

This test measures your body’s natural production of C-peptide, a marker linked to insulin secretion, after eating a high-protein meal. It helps assess how well your pancreas responds to food.

Quick summary

["This test evaluates your body’s insulin production after eating."]

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

Key facts at a glance

LOINC
95085-7
Short code
C peptide 3.5h p meal SerPl-mCnc
Synonyms
C peptide 3.5h 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 symptoms of diabetes, insulin resistance, or unexplained weight changes. It can also help diagnose conditions like Cushing’s syndrome or other hormonal imbalances affecting metabolism.

What to Expect Before the Test

You’ll fast overnight (typically 8–12 hours) and then consume a high-protein meal before the blood draw. Blood samples are taken at scheduled intervals to measure C-peptide levels over time.

What the Results Mean

C-peptide levels reflect your pancreas’s ability to produce insulin naturally. Abnormal results may indicate issues like diabetes, pancreatic disorders, or metabolic syndrome.

Common Conditions This Test Helps Diagnose

This test helps identify diabetes, insulinoma (a rare tumor affecting insulin), or conditions where insulin production varies (e.g., prediabetes). It’s also used to monitor treatment responses in some cases.

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: How Results Guide Care

Short name

C-peptide meal test

Frequently asked questions

How long does the test take to process results?
Results are typically available within 1–3 business days, depending on your lab. Follow-up with your doctor to discuss findings and next steps.
Can I eat or drink anything before the blood draw?
No, you must fast except for water until after the meal. Avoid alcohol or sugary drinks before testing.
Will the meal affect my daily routine?
Yes, you’ll need to plan around the meal timing, but it’s temporary. Your doctor will guide you on when to eat and when to schedule the blood tests.
  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