- urine creatinine - spot collection
This test measures the amount of creatinine in a urine sample that may either be from a single sample of urine or from a 24 hour collection.
Who is a candidate for the test?
The collection is performed on 2 types of people: as a measure of how well the kidneys are working (as a clearance) or as a measure of the adequacy of a urine collection that is used to check other products in the same sample (like calcium or uric acid in someone who has kidney stones).
How is the test performed?
Either a 24-hour urine sample or a single ("spot") sample may be done. For a spot sample, the person urinates and collects a small sample in a container. The container is sealed and given to the healthcare provider.
For a 24-hour urine sample, the person should follow the specific instructions of the healthcare professional.
In general, this or a similar schedule is followed:
What is involved in preparation for the test?
The person should request specific instructions from the healthcare professional. If the test is done as part of a study for kidney stones, it may include a special diet.
What do the test results mean?
The healthy range for creatinine in urine is:
- spot collection, 25 to 400 milligrams/deciliter (mg/dL)
- 24-hour sample, 0 to 0.25 grams per 24 hours
The amount of creatinine excreted in the urine is usually a constant for a person at a given weight. If kidney damage occurs, the creatinine in the blood changes by increasing. So, in order to interpret a urine creatinine, calculations also using a blood creatinine are necessary. (see kidney function tests and creatinine clearance)