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: C-Peptide 35 Hour Glucose Serum or Plasma Mass Concentration

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

: This test measures C-peptide in a blood sample after a 35-hour glucose preparation or challenge, helping assess how much insulin your pancreas is producing.

Quick summary

[": C-peptide reflects your body's own insulin production and is often used to evaluate beta-cell function and distinguish types of diabetes."]

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

Key facts at a glance

LOINC
58508-3
Short code
C peptide 3.5h p Glc SerPl-mCnc
Synonyms
C peptide 3.5h 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?

: C-peptide is a small protein released by the pancreas alongside insulin. Because it stays in the blood longer than insulin, it gives a useful estimate of how much insulin your body is naturally making.

: Why the Glucose Component?

: A glucose preparation or challenge is used to stimulate the pancreas so C-peptide levels can be assessed under controlled conditions. The exact protocol and timing should be confirmed with your ordering laboratory.

: How the Sample Is Collected

: A blood sample is typically drawn from a vein in your arm. Your care team will explain whether fasting or specific timing is required before the draw.

: What the Results Mean

: Higher or lower C-peptide levels can suggest different patterns of insulin production. Results are interpreted by your clinician alongside blood glucose, symptoms, and other tests.

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.

: C-peptide testing is used to evaluate pancreatic beta-cell function, help distinguish type 1 from type 2 diabetes in some cases, and investigate suspected insulin-producing conditions. It does not by itself diagnose a condition and must be interpreted with clinical context.

Short name

: C-Peptide (35-h Glucose)

Frequently asked questions

: Do I need to fast for this test?
: Fasting and timing requirements depend on the specific protocol ordered. Follow the instructions given by your clinician or laboratory.
: Is C-peptide the same as insulin?
: No. C-peptide is released together with insulin but is measured separately because it reflects your body's own insulin production more reliably.
: Can I take this test at home?
: No, this test requires a blood draw performed by a trained healthcare professional, usually in a clinic or laboratory setting.
  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