Creatinine Test (Kidney Function)
Reviewed
Also called: Serum creatinine, Blood creatinine, Urine creatinine, Renal function
This test measures creatinine levels in a sample of your blood and/or urine (pee). If blood and/or urine creatinine levels are not normal, it may be a sign of kidney disease.
Specimen: Blood and/or urine
Why this test may be ordered
- Checking kidney health
- Diagnosing or monitoring kidney disease
- Monitoring medicines or conditions that can affect kidneys
Preparation and collection
Your provider will let you know how to prepare for your test. You may be told to not eat meat for 24 hours before your test.
A health care professional will take a blood sample from a vein in your arm, using a small needle. For a creatinine urine test: You may need to provide all the urine you pass over 24 hours.
There is very little risk to having a blood test. There is no risk to having a urine test.
Understanding results
Creatinine levels that are considered normal for you will depend on how much muscle you have, what you eat, your age, and how active you are.
What does high creatinine mean?
High creatinine (high for you): High for you, it may be a sign of: Kidney disease or injury, including infection, poor blood flow to the kidneys, a blockage in the urinary system, or kidney failure. Limitation: High blood creatinine levels don't always mean you have a kidney problem. They may be caused by dehydration, muscle disorders and injuries, muscular dystrophy, intense exercise, or a diet high in meat. Next step: You will likely need to be retested and/or have other tests, too.What does low creatinine mean?
Low creatinine (low for you): Low for you, it may be a sign of malnutrition or a condition that causes your muscles to get smaller, such as a long illness, a nerve disorder, or muscle loss from aging. Serious liver disease can also lead to low levels. Limitation: Low levels of blood creatinine aren't common. Next step: You will likely need to be retested and/or have other tests, too.- Normal creatinine: If you're healthy, your levels are usually fairly stable over time. Limitation: But a normal creatinine test result doesn't always mean that your kidneys are healthy. Sometimes, blood creatinine levels remain in a normal range during the early stages of kidney disease. Next step: If your provider suspects you have a kidney condition, you will likely have other kidney tests even if your creatinine results seem normal.
- eGFR is an estimate and may be less reliable in unusual muscle mass or rapidly changing kidney function.
- Meat intake, supplements, intense exercise, hydration, and medicines can affect creatinine.
What to do next
If your results are abnormal, a single high creatinine test can't diagnose a specific condition. You will likely need to be retested and/or have other tests, too.
- Which reference interval and units apply to my result?
- Could medicines, supplements, illness, or sample timing affect this result?
- Do I need a repeat test or another test before any conclusion is made?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.
U.S. National Library of Medicine: Creatinine Test (Kidney Function)