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C-peptide (Serum) with High-Performance Liquid Chromatography (HPLC) Measurement

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

This test measures the amount of C-peptide, a small protein produced along with insulin by your pancreas. It helps assess how much insulin your body naturally makes.

Quick summary

["C-peptide helps evaluate insulin production and diabetes management."]

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

Key facts at a glance

LOINC
58509-1
Short code
C peptide 3.5h p Glc SerPl-sCnc
Synonyms
C peptide 3.5h p Glc SerPl-sCnc
Category
glucose
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
true
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 a C-peptide test to check if your pancreas is producing enough insulin. It’s often used to diagnose type 1 or type 2 diabetes, monitor insulin-dependent conditions, or assess how well insulin therapy is working. Some people also get it to rule out other causes of high or low blood sugar levels.

How the Test Works

A small blood sample is taken from a vein in your arm. The sample is sent to a lab where it’s analyzed using high-performance liquid chromatography (HPLC), a precise method to measure tiny amounts of C-peptide in your serum.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a broader glucose study. Wear comfortable clothing and plan to stay near the testing site for a short time.

What the Results Mean

Results help doctors understand how your pancreas is functioning. Low levels may suggest insulin deficiency, while high levels could indicate overproduction of insulin or other conditions. Your doctor will interpret the results in the context of your overall health.

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

Short name

C-peptide level

Frequently asked questions

What does a low C-peptide level mean?
A low C-peptide level often means your pancreas isn’t producing enough insulin naturally, which can be a sign of type 1 diabetes or insulin resistance. It may also help confirm whether insulin therapy is needed or if another condition is affecting blood sugar.
What does a high C-peptide level mean?
High C-peptide levels can occur in people with type 2 diabetes who still produce some insulin, or in those with other metabolic issues. It may also appear in cases of insulinoma (a rare tumor that causes excessive insulin production). Your doctor will discuss these findings with you.
Can C-peptide test results change over time?
Yes, C-peptide levels can fluctuate based on factors like diet, exercise, stress, or underlying health conditions. Regular monitoring helps track how well your body’s insulin production is responding to treatment or lifestyle changes.
  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