C-Peptide plasma/serum

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Auckland Te Toka Tumai

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C-Peptide plasma/serum

Testing Laboratory

Auckland Te Toka Tumai | Auckland Hospital

Department

Chemical Pathology

Delphic Registration Code (Alpha Code)

CPSN

Test Code (Numeric Code)

5027

Laboratory Handling

Registration

If sample arrives frozen please thaw and hand to 8100 operator.

Separating

Separate within 4 hours

Sample Stability

4 hours at 15-25°C, 24 hours at 2-8°C, 30 days at -20°C

Synonyms

C-Peptide, Serum C-Peptide

Turnaround Time

3 hours

Specimen Type

Plasma
Serum

Specimen Requirements

Tube/Container Type:

Preferred

Lithium Heparin PST- Gel (Light Green Cap)

Acceptable

Heparin (Microtainer)
EDTA (Lavender Cap)
Lithium Heparin - Non-gel (Green Cap)
Lithium Heparin PST- Gel (Light Green Cap)
Plain (Red Top)
SST II (Gold Cap)

Preferred Sample Volume (ml)

4.5

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

Heparin (Microtainer)

Acceptable

EDTA (Microtainer)
EDTA (Lavender Cap)
Lithium Heparin - Non-gel (Green Cap)
Lithium Heparin PST- Gel (Light Green Cap)
Plain (Red Top)
SST II (Gold Cap)

Minimum Sample Volume (ml)

0.5

Additional Specimen Information

4.5 mL Adult PST Blood (Preferred)
Micro-PST 1.5 mL Paediatric Micro-PST Blood (Preferred)
EDTA 4 mL EDTA Blood
Heparin 5 mL Heparin Plasma
Plain 4 mL Plain Serum
SST 3.5 mL Adult SST Blood
Microsample 1.5 mL Paediatric Microsample Blood

Diagnostic Use

C-peptide is the 31 amino acid peptide segment released from proteolytic breakdown of Proinsulin to Insulin in pancreatic beta cells. There is equimolar secretion of C-peptide and insulin into the portal vein. However, in the systemic circulation the fasting C-peptide level is about 5 – 15 times higher than insulin, due to negligible extraction in the liver and peripheral tissues. C-peptide is primarily degraded in the kidneys so its level is elevated in renal failure.

In hypoglycaemic states, C-peptide level can help to identify the cause: patients with endogenous overproduction of insulin (e.g. insulinoma or sulphonylurea intoxication) have high insulin as well as high C-peptide levels (Insulin to C-peptide molar ratio 1. To convert Insulin in mU/L to pmol/L, multiply insulin result by 6.95.

C-peptide testing should not be used to diagnose diabetes mellitus. In both type 1 diabetes or long standing type 2 diabetes with absolute insulin deficiency, the C-peptide level can be low. In a patient with recently diagnosed diabetes or insulin-treated diabetes in whom the diagnosis of T1D is being considered, a random C-peptide 7 mmol/L, reduces the need for pursuing antibody support for a clinical diagnosis of T1D. Please note that the testing of antibodies for prediction of T1D (in those without diabetes) is not clinically indicated, and should only be done within clinical trial settings.

C-peptide measurement can also be useful in follow up evaluations after pancreatectomy and post-pancreatic transplantation to measure pancreatic beta cell secretory reserve. C-peptide measurement after an overnight 8 hour fast or mixed meal tolerance test can help to assess beta cell secretory capacity.

In patients with insulin resistance, early type 2 diabetes mellitus or endocrine disorders like Cushing’s syndrome and Acromegaly, both insulin and C-peptide levels are raised. However, testing C-peptide level under these settings is generally not clinically useful and will need prior approval.

References:

Mayo Medical Laboratories Test Catalog ( https://www.mayomedicallaboratories.com/test-catalog/Overview/8804,last accessed 28/12/17)
Lab Tests online ( https://labtestsonline.org/tests/c-peptide , last accessed 28/12/17)
Henry’s clinical diagnosis and management by laboratory methods (23rd edition), Chapter 16 P.206-207

Reference Intervals

Units : pmol/L

Reference interval (fasting): 370 – 1470 (after overnight fast)

Ng/ mL x333 =pmol/L

Test Method

Test performed by: LabPLUS Automation
Analysed on Cobas Line 2.5
Principle: Chemiluminesent
Analyser: Cobas

Uncertainty of Measurement

Uncertainty of Measurement : 8%

Last updated: 12/03/2026

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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #

Testing Laboratory

Department

Delphic Registration Code (Alpha Code)

Test Code (Numeric Code)

Laboratory Handling

Registration

Separating

Sample Stability

Synonyms

Turnaround Time

Specimen Type

Specimen Requirements

Tube/Container Type:

Preferred

Acceptable

Preferred Sample Volume (ml)

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

Acceptable

Minimum Sample Volume (ml)

Additional Specimen Information

Aliquot Instructions

Sample Type

Transport to Lab

Additional Referral/Aliquot Information

Diagnostic Use

Reference Intervals

Test Method

Uncertainty of Measurement

Contact Information

Enquiry Form

Search tests

C-Peptide plasma/serum

Overview

Testing Laboratory

Department

Delphic Registration Code (Alpha Code)

Test Code (Numeric Code)

Laboratory Handling

Registration

Separating

Sample Stability

Synonyms

Turnaround Time

Specimen

Specimen Type

Specimen Requirements

Tube/Container Type:

Preferred

Acceptable

Preferred Sample Volume (ml)

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

Acceptable

Minimum Sample Volume (ml)

Additional Specimen Information

Referral

Aliquot Instructions

Sample Type

Transport to Lab

Additional Referral/Aliquot Information

Clinical Information/Test Method

Diagnostic Use

Reference Intervals

Test Method

Uncertainty of Measurement

Contact Information

Contact Information

Enquiry Form

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