This test measures the level of a substance called creatinine in your urine.
Creatinine is a waste product that your body makes when you use your muscles. It's also made when your body digests meat. Healthy kidneys remove creatinine from your blood, and it leaves your body in your urine.
This test can find out whether your kidneys are working normally or to see if treatment for kidney disease is working.
You may need this test if your healthcare provider suspects you have a problem with your kidneys. Signs and symptoms of kidney disease include:
Swelling in your feet or ankles
Puffiness around your eyes
Dry, itchy skin
Blood or protein in your urine
You may also have this test if you have already been diagnosed with chronic kidney disease, so that your healthcare provider can check your kidney function regularly and adjust your treatment if needed.
Your healthcare provider may also order a protein-to-creatinine ratio test done on your urine. This will look at the amount of protein compared with creatinine. Excess protein that has leaked into your urine may be a sign of kidney disease.
Your healthcare provider may also order blood tests to measure your kidney function. These might include a creatinine blood test and a blood urea nitrogen, or BUN, test. The creatinine blood test is used to find out your creatinine clearance, which gives a good measure of kidney function.
Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you.
Results are given in grams per day (g/day) or millimoles per day (mmol/day). Normal results depend on your muscle mass and age. Ranges differ for men and women:
Male: 0.8 to 1.8 g/day (7 to 16 mmol/day)
Female: 0.6 to 1.6 g/day (5.3 to 14 mmol/day)
Higher levels may mean that you have kidney disease.
This test needs a urine sample. Your healthcare provider may need a "spot" urine test or a 24-hour test.
For a "spot" urine test, you collect one sample, preferably early in the morning.
For a 24-hour urine sample, you must collect all the urine you produce for 24 hours. Empty your bladder completely first thing in the morning without collecting it. Note the time. Then collect your urine every time you go to the bathroom over the next 24 hours. Keep the urine in the refrigerator or in a cool place after each collection.
This test poses no known risks.
If you are muscular, your urine creatinine level may be higher than normal. If you are of small stature or have little muscle mass because of disease, your urine creatinine level will likely be lower than normal.
Your urine creatinine level may be higher if you are African American, Hispanic, Asian, Pacific Islander, or American Indian.
Certain medicines may also affect your results.
You don't need to prepare for this test. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.