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Test ID CTU Creatinine, 24 Hour, Urine

Useful For

Urinary creatinine, in conjunction with serum creatinine, is used to calculate the creatinine clearance, a measure of renal function.

Method Name

Enzymatic Colorimetric Assay

Reporting Name

Creatinine, U

Specimen Type

Urine

Container/Tube: Plastic, 5-mL tube (T465)

Specimen Volume: 4 mL

Collection Instructions:

1. Collect urine for 24 hours.

2. Refrigerate specimen within 4 hours of completion of 24-hour collection.

Additional Information:

1. 24-Hour volume is required.

2. This test does not require the use of a chemical preservative; if a chemical preservative is used, it must be added to the specimen within 4 hours of completion of 24-hour collection.

3. See the urine preservative collection options for acceptable preservatives when submitting specimen for multiple tests.

 

Urine Preservative Collection Options

Ambient

Yes

Refrigerated

Preferred

Frozen

Yes

6N HCl

Yes

50% Acetic Acid

Yes

Na2CO3

Yes

Toluene

Yes

6N HNO3

Yes

Boric Acid

Yes

Thymol

Yes

 

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Refrigerated (preferred) 30 days
  Ambient  30 days
  Frozen  30 days

Clinical Information

Creatinine is formed from the metabolism of creatine and phosphocreatine, both of which are principally found in muscle. Thus the amount of creatinine produced is in large part dependent upon the individual's muscle mass and tends not to fluctuate much from day-to-day.  

 

Creatinine is not protein-bound and is freely filtered by glomeruli. All of the filtered creatinine is excreted in the urine. Renal tubular secretion of creatinine also contributes to a small proportion of excreted creatinine. Although most excreted creatinine is derived from an individual's muscle, dietary protein intake, particularly of cooked meat, can contribute to urinary creatinine levels.

 

The renal clearance of creatinine provides an estimate of glomerular filtration rate.

Reference Values

Normal values mg per 24 hours:

Males: 955-2936 mg/24 hours

Females: 601-1689 mg/24 hours

 

Reference ranges for male and female patients <18 and >83 years of age have not been established.

 

The expected urine creatinine excretion per 24 hours:

 

Males: 13-29 mg/kg of body weight/24 hours

Females: 9-26 mg/kg of body weight/24 hours

 

Reference ranges for male and female patients <18 and >83 years of age have not been established.

 

Note: To convert to mg/kg of body weight/24 hours, divide the mg/24 h result by body weight in kg.

Cautions

The reliability of 24-hour urinary creatinine determinations are, as for all timed urine collections, very dependent on accurately collected 24-hour specimens.  

 

Intraindividual variability in creatinine excretion may be due to differences in muscle mass or amount of ingested meat.  

 

Acute changes in GFR, before a steady state has developed, will alter the amount of urinary creatinine excreted.

Day(s) Performed

Monday through Sunday; Continuously

Report Available

1 day

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

82570

NY State Approved

Yes