What is a creatinine test?
This test measures creatinine levels in blood and/or urine. Creatinine is a waste product made by your muscles as part of regular, everyday activity. Normally, your kidneys filter creatinine from your blood and send it out of the body in your urine. If there is a problem with your kidneys, creatinine can build up in the blood and less will be released in urine. If blood and/or urine creatinine levels are not normal, it can be a sign of kidney disease.
Other names: blood creatinine, serum creatinine, urine creatinine
What is it used for?
A creatinine test is used to see if your kidneys are working normally. It’s often ordered along with another kidney test called blood urea nitrogen (BUN) or as part of a comprehensive metabolic panel (CMP). A CMP is a group of tests that provide information about different organs and systems in the body. A CMP is frequently included in a routine checkup.
Why do I need a creatinine test?
You may need this test if you have symptoms of kidney disease. These include:
- Puffiness around the eyes
- Swelling in your feet and/or ankles
- Decreased appetite
- Frequent and painful urination
- Urine that is foamy or bloody
You may also need this test if you have certain risk factors for kidney disease. You may be at higher risk for kidney disease if you have:
What happens during a creatinine test?
Creatinine can be tested in blood or urine.
For a creatinine blood test:
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
For a creatinine urine test:
Your health care provider will ask you to collect all urine during a 24-hour period. Your health care provider or a laboratory professional will give you a container to collect your urine and instructions on how to collect and store your samples. A 24-hour urine sample test generally includes the following steps:
- Empty your bladder in the morning and flush that urine away. Record the time.
- For the next 24 hours, save all your urine passed in the container provided.
- Store your urine container in the refrigerator or a cooler with ice.
- Return the sample container to your health provider’s office or the laboratory as instructed.
Will I need to do anything to prepare for the test?
You may be told to not eat cooked meat for 24 hours before your test. Studies have shown that cooked meat can temporarily raise creatinine levels.
Are there any risks to the test?
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
There is no risk to having a urine test.
What do the results mean?
In general, high levels of creatinine in blood and low levels in urine indicate kidney disease or another condition that affects kidney function. These include:
But abnormal results don’t always mean kidney disease. The following conditions can temporarily raise creatinine levels:
- Intense exercise
- A diet high in red meat
- Certain medicines. Some medicines have side effects that raise creatinine levels.
If you have questions about your results, talk to your health care provider.
Is there anything else I need to know about a creatinine test?
Your health care provider may also order a creatinine clearance test. A creatinine clearance test compares the level of creatinine in blood with the level of creatinine in urine. A creatinine clearance test may provide more accurate information on kidney function than a blood or urine test alone.