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C-peptide (Serum) with 24-Hour Urine Collection for Glucose

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

This test measures your body’s natural production of C-peptide, a marker of insulin release, and evaluates how much glucose (sugar) you excrete in urine over 24 hours.

Quick summary

["Helps assess insulin function and glucose metabolism together."]

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

Key facts at a glance

LOINC
47592-1
Short code
C peptide 5M p Glc SerPl-sCnc
Synonyms
C peptide 5M 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

Your doctor may order this test to diagnose or monitor conditions like diabetes, insulin resistance, or pancreatic issues. It also helps distinguish between types of diabetes or check how well insulin is working in your body.

What to Expect Before the Test

For the serum C-peptide measurement, you’ll provide a blood sample. For the urine glucose test, collect all urine for 24 hours in a special container. Follow your doctor’s instructions carefully to ensure accurate results.

How the Test Works

The blood test checks your C-peptide levels, a protein linked to insulin production. The urine test measures total glucose lost over a day, helping assess how your body handles sugar.

What the Results Mean

High C-peptide levels may indicate overproduction of insulin, while low levels could suggest poor insulin function. Elevated urine glucose suggests uncontrolled blood sugar, possibly from diabetes or other metabolic 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.

◆Associated findings1

Frequently asked questions

What does a normal C-peptide level mean in this test?
A normal C-peptide level alone doesn’t define ‘normal’ for this combined test, as it’s interpreted alongside urine glucose results. Your doctor will review both together to assess your metabolic health.
Why is urine glucose measured in 24-hour collections?
A 24-hour urine collection gives a full picture of how much glucose your body excretes, which can reveal patterns of sugar loss—useful for diagnosing diabetes or tracking how well medications control blood sugar over time.
Can I drink water during the urine collection?
Yes, but avoid excessive water intake, as it may dilute urine and affect results. Follow your doctor’s specific instructions for the best accuracy.
  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