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Creatinine Clearance (from 24-hour urine collection)

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

This test measures how well your kidneys filter waste products, specifically creatinine, over a full day. It helps assess kidney function and blood flow to the kidneys.

Quick summary

["A 24-hour urine test helps doctors check how well your kidneys are working by tracking waste removal over time."]

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

Key facts at a glance

LOINC
35941-4
Short code
CT Ankle-Bl
Synonyms
CT Ankle-Bl
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ct
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 if they suspect kidney problems, such as chronic kidney disease, or if you have conditions like high blood pressure or diabetes that can affect kidney function. It’s also used to monitor kidney health before or after treatments like chemotherapy or surgery.

What to Expect Before the Test

You’ll need to collect all urine for a full 24-hour period, starting after you wake up and ending just before you wake up the next day. Drink plenty of fluids but avoid caffeine or large amounts of salt. Store your urine samples in a refrigerator and return them to your lab on the same day.

What Happens During the Test

No special preparation is needed beyond collecting urine samples at home. The lab will analyze the total creatinine in your urine and compare it to a blood sample taken at the same time to calculate your creatinine clearance.

What the Results Mean

Lower than expected clearance may indicate kidney damage or reduced blood flow. Higher values could suggest dehydration or overhydration. Your doctor will interpret results in relation to your overall health and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

24-Hour Urine Creatinine Clearance

Frequently asked questions

How often should I get this test?
This test is typically done once or twice a year if you have chronic kidney disease or risk factors. Your doctor will determine the frequency based on your health needs and symptoms.
Can I eat or drink anything special before the test?
No special diet is required, but avoid caffeine or large salt intake to avoid influencing results. Follow your doctor’s instructions for fluid intake.
What if I miss any urine sample during the 24-hour period?
If you miss any urine, you’ll need to restart the collection from the next morning. Missing samples can affect accuracy, so it’s important to complete the full 24-hour period.
  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