What Is a Creatinine Urine Test?
Creatinine is a normal waste product produced by muscle metabolism. When your kidneys are functioning normally, they filter creatinine and other waste products out of your blood and send them out of the body through urine.
A creatinine urine test measures the amount of creatinine in your urine and can help your doctor evaluate how well your kidneys filter waste. This is useful in diagnosing or ruling out kidney diseases and some other conditions.
Your doctor may use a random urine sample, but most likely will order a urine 24-hour volume test. This noninvasive creatinine urine test does not cause pain, and there are no risks associated with the procedure.
Preparing for the 24-Hour Volume Test
The 24-hour volume test is noninvasive and involves only the collection of urine. Before the test:
- Tell your doctor if you are pregnant or think you may be pregnant.
- List your prescription and over-the-counter medications and supplements and ask if any of these will interfere with the results.
- Based on the reasons for the test, your doctor may advise you to avoid certain foods or beverages during the test.
- Ask if you must begin the test at a particular time of day.
- Make sure you understand when and where you should return the container.
- No fasting or medications are required.
- Since this test involves collecting and storing urine for a 24-hour period, you may want to consider scheduling the test for a day when you are at home or not on the go.
- You will be given one or more containers for collecting and storing urine.
The 24-Hour Volume Test Procedure
To perform the test, you will use a special urine collection container to collect one day’s worth of urine. Failure to follow instructions could lead to false results, and you may have to repeat the procedure.
The test should begin at a specific time and end at the same time on the following day.
- Your test must begin in the morning. On the first day, do not collect your first morning urine, but note and record the time.
- Collect all your urine for the next 24 hours, keeping the storage container refrigerated.
- Collect your first morning urine on the second day at the same time you began the test yesterday.
- Keep the container refrigerated until it is time to return it. Make sure the cover on the container is tight and return it promptly to the lab or doctor’s office as instructed.
- Be sure to notify your healthcare provider if you were unable to follow all instructions. Report missed urine, spilled urine, urine collected after the 24-hour time period ended, or if you were unable to store the collection bottle in a cool place.
Since you are simply collecting urine, there are no health risks or side effects associated with the 24-hour urine test.
Interpreting the Results of a Creatinine Urine Test
There are natural variations in creatinine output due to age and body mass—the more muscular you are, the higher your range will be. Generally, normal urine creatinine values range from 500 to 2,000 mg per day. It is important to note that not all laboratories use the same values, and results are dependent upon the proper collection of the urine sample.
Creatinine values that fall outside the normal range may be an indication of:
- kidney disease
- kidney infection
- kidney failure
- urinary tract obstruction, such as kidney stones
- late-stage muscular dystrophy
- myasthenia gravis (an autoimmune disease)
Abnormal values can also occur during pregnancy, in patients who have diabetes mellitus, and in people who have a diet high in meat.
It is very difficult to evaluate the results on your own, so it is important to discuss your specific results with your doctor.
A blood test called a serum creatinine test or blood creatinine test can be used to measure the amount of creatinine that is in your blood.