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C-peptide (Serum/Plasma, Mass Concentration)

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

This test measures the amount of C-peptide, a small protein produced by your pancreas along with insulin during blood sugar regulation.

Quick summary

["C-peptide helps assess how much insulin your body naturally produces."]

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

Key facts at a glance

LOINC
58514-1
Short code
C peptide 45M p Glc SerPl-mCnc
Synonyms
C peptide 45M p Glc SerPl-mCnc
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

What Is C-Peptide Used For?

C-peptide is primarily used to evaluate insulin production and diagnose conditions like diabetes or pancreatic issues. It helps distinguish between diabetes caused by insufficient insulin (Type 1) versus insulin resistance (Type 2).

How Is This Test Performed?

A blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab for analysis using a specialized immunoassay method to measure C-peptide levels.

Why Might You Need This Test?

Your doctor may order this test if you have diabetes symptoms, unexplained weight loss, or if insulin levels appear abnormal. It’s also used in pregnancy to monitor gestational diabetes or to check for pancreatic tumors.

What Do Results Mean?

Results help determine if your body produces enough insulin naturally. Low levels may indicate Type 1 diabetes or insulin deficiency, while high levels could suggest overproduction or certain pancreatic disorders.

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 is a biomarker for insulin secretion. It’s critical in diagnosing diabetes subtypes, assessing pancreatic function, and guiding treatment plans, especially in cases where insulin therapy is involved.

Short name

C-peptide level

Frequently asked questions

Why do I need this test if I already have diabetes?
Even with diabetes, C-peptide levels can help confirm whether your condition is due to insufficient insulin production (Type 1) or insulin resistance (Type 2). It may also be used to monitor pancreatic health or rule out other conditions like pancreatic cancer.
How long does it take to get my results?
Results typically arrive within 1–3 business days, depending on your lab’s processing time. Your doctor will contact you once they’re ready.
Can I eat or drink before this test?
You may eat and drink normally unless instructed otherwise by your doctor. Fasting is not required for this test.
  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