What is a Creatinine Clearance Test?

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  • Written By: Nat Robinson
  • Edited By: Heather Bailey
  • Last Modified Date: 04 October 2019
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A creatinine clearance test is done to analyze how well the kidneys are filtering waste from the blood. This type of test measures the level of creatinine in the blood, as well as the urine. Creatinine is a type of waste found in the body in small amounts. It is a breakdown of creatine, which is used by the muscles. There are structures in the kidneys known as glomeruli, which filter excess waste, such as excessive creatinine, from the bloodstream through urine.

If creatinine levels become very elevated, this could mean there is a problem with a person's kidney function. The problem could range from a kidney infection to the beginning of kidney failure. A creatinine clearance test may be done on a person exhibiting symptoms of a kidney problem. The symptoms may include flank pain, frequent urination, swelling and fatigue. If an individual has a pre-diagnosed kidney disease, he or she may undergo this test to check the disease's progression.


The first part of a creatinine clearance test usually involves a blood test. To have this done, the patient may report to a hospital or laboratory to have blood withdrawn. The blood will be closely analyzed and the amount of creatinine present will be calculated and recorded. For most individuals, the insertion of the needle to withdraw the blood is the most uncomfortable part of this phase of the creatinine clearance. In some cases, the blood test may be done again following the second phase of the test.

For the second part of the creatinine clearance, a urine sample is collected over the course of 24 hours. During this portion of the test, an individual will be asked to collect his or her urine privately over the course of one entire day. As creatinine levels may change through out a day, a full day's analysis should provide an acceptable average of the amount of creatinine present in the urine. Usually, the health care professional will provide a special container to the patient and will inform him or her if any particular directions will need to be followed while collecting the specimens. This may include noting the time at certain intervals during the sample.

When taking a creatinine clearance test, certain existing health conditions may be taken into consideration. For instance, certain health ailments may change the amount of creatinine a person has in his or her blood. This may include an existing kidney disease, diabetes, an infection or hypertension. In addition, an abnormality in the glomeruli or kidney's filtering structures can alter creatinine levels as well.

At the conclusion of a creatinine clearance test, a health care professional will be able to calculate the individual's glomerular filtration rate (GFR). This is the rate at which the glomeruli clears creatinine waste from the blood. The rate may be used to analyze the healthiness of the kidney's and in particular, their ability to filter blood adequately. When creatinine levels in the blood and urine are extremely unbalanced, the person may be prescribed medication. If the levels are so high that the person is in danger of going into kidney failure, more invasive treatment such as dialysis may be given.


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