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Creatinine, 12-Hour Urine, Quantitative

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

Measures the amount of creatinine in urine collected over 12 hours to help evaluate kidney function and check the completeness of the collection.

Quick summary

["This test measures creatinine excretion over 12 hours and can help assess kidney function when interpreted with other tests."]

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

Key facts at a glance

LOINC
33859-0
Short code
GH/Creat 12h Ur-Rto
Synonyms
GH/Creat 12h Ur-Rto
Category
kidney
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What is this test?

This test measures creatinine, a waste product produced by the muscles, in urine collected for 12 hours. The result may be reported as a urine concentration, total amount excreted, or an excretion rate.

Why might I need this test?

A timed urine creatinine measurement can help assess kidney function and determine whether the urine collection captured the full amount expected. It may be used alongside blood creatinine, estimated glomerular filtration rate, or urine protein testing.

How is the test performed?

Urine is collected into a labeled container for exactly 12 hours. The laboratory then measures the creatinine concentration and uses the collection time and urine volume to calculate the amount or rate of creatinine excretion.

How do I prepare for the test?

Follow the collection instructions provided by your healthcare professional, including the start and stop times. Keep the container closed and refrigerate it if instructed; report any missed urine or collection problems to the laboratory.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

12-Hour Urine Creatinine

Frequently asked questions

Why is urine collected for 12 hours?
A timed collection accounts for urine produced throughout the period. This allows the laboratory to calculate how much creatinine your body excreted rather than relying only on the concentration in one sample.
Does this test diagnose kidney disease on its own?
No. Results are usually interpreted with blood creatinine, estimated filtration rate, urine protein, other relevant tests, and the collection record.
What happens if part of the urine collection is missed?
The result may not accurately reflect your full 12-hour creatinine excretion. Tell the laboratory about a missed collection, because the result may need to be repeated or interpreted cautiously.
  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