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Fasting and Meal-Stimulated C-Peptide, Serum/Plasma — Panel

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

Measures C-peptide released with insulin before and after a meal or glucose load to assess pancreatic insulin production.

Quick summary

["This panel helps evaluate insulin production and may help clarify diabetes or unexplained low blood sugar."]

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

Key facts at a glance

LOINC
95080-8
Short code
C peptide p Cfst + meal Pnl SerPl
Synonyms
C peptide p Cfst + meal Pnl SerPl
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
44
Ref high
147
Critical range
— – 5 N/A
Fasting
true
Population
adult
Sex
all
Age range
18–65 years
CPT
84075
SNOMED
27550007
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

What is this test?

C-peptide is a substance produced by the pancreas when it releases insulin. This panel measures C-peptide in blood, usually along with glucose, before and after a meal or a specified glucose load.

Why might I need this test?

C-peptide testing may be used to assess how well the pancreas produces insulin, help evaluate diabetes or prediabetes, and investigate episodes of unusually low blood sugar. It can also help determine whether excess insulin is coming from the pancreas or another source.

How is the test performed?

A healthcare professional draws blood from a vein. For a meal-stimulated or glucose-stimulated test, samples may be collected after an overnight fast and again at a specified time after the patient receives a meal or glucose drink.

How do I prepare for the test?

Follow the preparation instructions provided by the laboratory or your clinician. If a fasting sample is required, do not eat or drink anything other than water for the instructed number of hours, and remain available for the timed second sample.

Reference range

Adult: 44-147 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

C-Peptide Fasting and Meal-Stimulated Panel

Frequently asked questions

What does a C-peptide blood test show?
It estimates how much insulin the pancreas is releasing because the body releases C-peptide and insulin in roughly equal amounts.
Why are C-peptide and glucose measured together?
The two results are more informative together because C-peptide shows insulin production while glucose shows the blood sugar level at the same time.
Is this the same as an insulin test?
No. An insulin test measures circulating insulin, while the C-peptide test helps evaluate the body's own insulin secretion, including insulin made by the pancreas.
  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