If your symptoms suggest that you may have kidney disease or damage you will need to undergo a series of tests. The 24-hour creatinine clearance test is one the tests your doctor may recommend to effectively diagnose your condition. It determines how well your kidneys are removing creatinine from your blood.

Creatinine is a waste product produced during muscle metabolism to create energy. It flows through the blood from muscles to the kidneys for excretion in urine. However, if you have kidney disease these filtering organs do not effectively remove creatinine from your blood.

By comparing the amount of creatinine in a 24-hour sample of urine to the blood serum creatinine levels, your doctor can use the creatinine clearance test to diagnose kidney disease and how well your kidneys are functioning.

If you have kidney disease the test can be used throughout the course of the disease to monitor kidney function, adjust your medication or treatment program, or check for kidney failure.

How to Take the Test

Your first urine elimination in the morning should be done into the toilet. After that you use a container from your doctor to collect a sample each time you urinate over a 24-hour period, including the first time you urinate the following morning. You must keep the container refrigerated during the collection period and take note of the dates and time. Be sure to hand it in to the lab as soon as possible after the test.

Fasting before the test isn't required. However, you may want to reduce the amount of protein you eat before the test, as protein intake can affect your creatinine levels. Also, some herbal supplements — such as spirulina and soy — are rich in protein so you should avoid taking them before the test and let your doctor know that they're a part of your diet.

Also, seek advice from your doctor about stopping any medications you're taking before the test. Some medications can influence your creatinine clearance test results including:

- diuretics or water pills
- some blood pressure medications
- some nonsteroidal anti-inflammatory drugs
- antibiotics such as gentamicin

How Is Creatinine Clearance Measured?

Creatinine clearance results are given in millilitres per minute. A normal range is 75 to 115 ml/min for women and 85 to 125 ml/min for men. Older people, pregnant women and athletes tend to have higher values.

If your results are higher than the normal range, it's possible that your kidneys are damaged and not functioning properly. However, lower results may also be a sign of other conditions such as dehydration, a bladder problem or heart failure.

Your doctor will recommend additional tests such as the estimated glomerular filtration rate (eGFR) test, or imaging tests such as an ultrasound, X-ray or computerized tomography (CT) scan to confirm the diagnosis.

If a combination of testing shows that you do have kidney damage, the earlier this is treated, the better. There are a wide range of natural therapies that both help to reverse kidney damage, and treat the cause of kidney damage, helping to protect the kidney from further loss of function. This can include herbal and nutritional supplements, plus dietary and lifestyle changes.