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C-peptide measured by high-performance liquid chromatography (HPLC) in plasma

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

This test measures C-peptide, a natural byproduct of insulin production, using a precise liquid chromatography method. It helps assess how well your pancreas is producing insulin.

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
47588-9
Short code
C peptide 2h p Glc SerPl-sCnc
Synonyms
C peptide 2h 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 Is This Test Done?

Doctors may order a C-peptide test to check if your body produces insulin normally. It can help diagnose diabetes, monitor treatment effectiveness, or investigate symptoms like fatigue, weight changes, or unexplained high blood sugar levels.

What Does It Measure?

C-peptide is released along with insulin when your pancreas makes it. Unlike insulin, which is broken down quickly, C-peptide stays in your bloodstream longer. This test measures its concentration to gauge insulin production.

How Is the Sample Collected?

A blood sample is taken from a vein, usually in your arm. You may feel a small pinch when the needle is inserted, but it usually doesn’t cause discomfort afterward.

What Are Common Uses?

C-peptide testing is often used to distinguish between type 1 and type 2 diabetes, check for insulin resistance, or evaluate pancreatic function in people with unexplained blood sugar issues.

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: C-peptide levels can indicate whether your body relies on insulin production or relies on external insulin therapy. Low levels may suggest insulin deficiency (e.g., type 1 diabetes), while normal or high levels can help rule out insulin resistance or other metabolic disorders.

Short name

C-peptide (HPLC)

Frequently asked questions

What does a C-peptide test tell me about my diabetes?
A C-peptide test helps determine if your diabetes is caused by insufficient insulin production (type 1) or insulin resistance (type 2). If your levels are low, it may mean your pancreas isn’t producing enough insulin naturally. If levels are normal or high, it may suggest your body is managing insulin differently.
How does this test differ from an insulin test?
Unlike insulin, which is broken down quickly, C-peptide remains stable in the blood. This makes C-peptide a more reliable marker for natural insulin production, as it reflects ongoing pancreatic function over time.
Can I fast before this test?
No fasting is required for a C-peptide test, but you should avoid eating or drinking anything (except water) for 2–4 hours before the blood draw to ensure 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