Turnaround Time: 1 day
CPT Code:


Test Type: 1 mL serum and 10 mL aliquot
Stability Time:



Room temperature

7 days


14 days


14 days

Freeze/thaw cycles

Stable x3

Reference Range:

• Male: younger than 12 years: 50−90 mL/minute, 12 years and older: 97−137 mL/minute

• Female: younger than 12 years: 50−90 mL/minute, 12 years and older: 88−128 mL/minute

Note: Creatinine clearance reference intervals are based on a body surface area of 1.73 m2.


Renal function test; estimate glomerular filtration rate (GFR); evaluate renal function in small or wasted subjects; follow possible progression of renal disease; adjust dosages of medications in which renal excretion is pivotal (eg, aminoglycosides, methotrexate, cisplatin)

Exercise may cause increased creatinine clearance. The glomerular filtration rate is substantially increased in pregnancy. Ascorbic acid, ketone bodies (acetoacetate), hydantoin, numerous cephalosporins1,2 and glucose may influence creatinine determinations. Trimethoprim, cimetidine, quinine, quinidine, procainamide reduce creatinine excretion. Icteric samples, lipemia, and hemolysis may interfere with determination of creatinine. Since tubular secretion of creatinine is fractionally more important in progressing renal failure, the creatinine clearance overestimates GFR with high serum creatinine levels. While ingestion of meats may cause some increase in creatinine excretion, in practice this seems to make little difference. Intraindividual variation in creatinine clearance is about 15%. Males excrete more creatinine and have slightly higher clearance than females.

Glomerular filtration rate declines about 10% per decade after age 50. Some patients with significant impairment of glomerular filtration rate have only slightly elevated serum creatinine.3 Creatinine clearance is calculated on the basis of the surface area of the patient. The estimated error of determining creatinine clearance utilizing serum and 24-hour urine collection has been found to be in the range of 10% to 15%. Any test requiring a 24-hour urine collection may also be run on this specimen (eg, protein, quantitative, 24-hour urine).

1. Swain RR, Briggs SL. Positive interference with the Jaffé reaction by cephalosporin antibiotics. Clin Chem. 1977 Jul; 23(7):1340-1342. PubMed 872385

2. Levey AS, Perrone RD, Madias NE. Serum creatinine and renal function. Annu Rev Med. 1988; 39:465-490 (review). PubMed 3285786

3. Klahr S. The modification of diet in renal disease study. N Engl J Med. 1989 Mar 30; 320(13):864-866. PubMed 2494456

Collection Details:

Patient Preparation:

Avoid cephalosporins. Have patient drink water before the clearance is begun, and continue good hydration throughout the clearance. If possible, drugs should be stopped beforehand.

Collection Instructions:

The test request form must state date and time collection started and date and time collection finished. The request form should state 24-hour urine volume.

Serum Preferred or plasma AND urine (24-hour)

Red-top tube, gel-barrier tube, green-top (heparin) tube and plastic urine container, with or without 6N HCl

Separate serum from cells within 45 minutes of collection. For urine, instruct the patient to void at 8 AM and discard the specimen. Then collect all urine including the final specimen voided at the end of the 24-hour collection period (ie, 8 AM the next morning). Screw the lid on securely. Tube must be labeled with patient's full name and date and time for a 24-hour collection. Submit both urine and serum simultaneously. It is preferable to collect the serum at the time the urine collection is completed or when the serum is brought to the draw station. The serum should be collected within 24 hours of the start or finish of the urine collection.

Room temperature.