Creatinine and Creatinine Clearance
Creatinine and creatinine clearance tests measure the level of the
creatinine (say "kree-AT-uh-neen") in your blood and urine. These tests tell
how well your kidneys are working.
Another substance, creatine (say "KREE-uh-teen"), is formed when food is changed into energy through a process called metabolism. Creatine is broken down into creatinine. Your kidneys take creatinine out of your blood and pass it out of your body in urine.
kidneys are damaged and can't work as they should, the amount of creatinine in your
urine goes down while its level in your blood goes up.
types of tests can be done.
Blood creatinine level
The blood creatinine level
shows how well your kidneys are working. A high level may mean your
kidneys are not working as they should. 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.
A creatinine clearance
test measures how well creatinine is removed from your blood by your kidneys. This test gives better information than a blood creatinine test
on how well your kidneys are working. The test is done on
both a blood sample and on a sample of urine collected over 24 hours.
Blood urea nitrogen-to-creatinine ratio (BUN:creatinine)
The BUN test measures the amount
of urea in your blood. Urea 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.
The levels of blood creatinine and
blood urea nitrogen (BUN) can be used to find the
BUN-to-creatinine ratio. This ratio can help your doctor check
for problems, such as dehydration, that may cause abnormal BUN and creatinine
Why It Is Done
These tests are done:
- To see if your kidneys are working
- To find out if your kidney disease is changing.
- To see how well the kidneys work in people who take medicines that can cause kidney
- To check for severe
dehydration. Dehydration generally causes
BUN levels to rise more than creatinine levels. This causes a high
BUN-to-creatinine ratio. Kidney disease or blocked urine flow from
your kidney causes both BUN and creatinine levels to rise.