Creatinine and Creatinine Clearance

Creatinine and creatinine clearance tests measure the level of the waste product Reference creatinine Opens New Window in your blood and urine. These tests tell how well your kidneys are working. The substance creatine is formed when food is changed into energy through a process called Reference metabolism Opens New Window. Creatine is broken down into another substance called creatinine, which is taken out of your blood by the Reference kidneys Opens New Window and then passed out of your body in urine. See a picture of the Reference kidneys Opens New Window Reference Opens New Window.

If your kidneys are damaged and can't work normally, the amount of creatinine in your urine goes down while its level in your blood goes up.

Three types of tests on creatinine can be done:

Blood creatinine level

The blood creatinine level shows how well your kidneys are working. A high creatinine level may mean your kidneys are not working properly. The amount of creatinine in the blood depends partly on the amount of muscle tissue you have; men generally have higher creatinine levels than women.

Creatinine clearance test

A creatinine clearance test measures how well creatinine is removed from your blood by your kidneys. A creatinine clearance test gives better information than a blood creatinine test on how well your kidneys are working. A creatinine clearance test is done on both a blood sample and on a sample of urine collected over 24 hours (24-hour urine sample).

Blood urea nitrogen-to-creatinine ratio (BUN:creatinine)

The levels of blood creatinine and Reference blood urea nitrogen (BUN) Opens New Window can be used to find the BUN-to-creatinine ratio. A BUN-to-creatinine ratio can help your doctor check for problems, such as dehydration, that may cause abnormal BUN and creatinine levels.

Reference Urea Opens New Window is a waste product made when protein is broken down in your body. Urea is made in the liver and passed out of your body in the urine. A blood urea nitrogen (BUN) test measures the amount of urea in your blood. Like creatinine, it can help your doctor see how well your kidneys are working.

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This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Reference Terms of Use. Reference How this information was developed to help you make better health decisions.