Test Details & Preparation
The creatinine blood test is used to assess kidney function. It is frequently ordered along with a BUN (blood urea nitrogen) test or as part of a basic or comprehensive metabolic panel (BMP or CMP), groups of tests that are performed to evaluate the function of the body's major organs. BMP or CMP tests are used to screen healthy people during routine physical exams and to help evaluate acutely or chronically ill people in the emergency room or hospital. Sometimes, creatinine may be performed as part of a renal panel to evaluate kidney function.
If the creatinine and BUN tests are found to be abnormal or if someone has an underlying disease that is known to affect the kidneys, such as diabetes or high blood pressure, then creatinine and BUN tests may be used to monitor for kidney dysfunction and the effectiveness of treatment. Blood creatinine and BUN tests may also be ordered to evaluate kidney function prior to some procedures, such as a CT (computed tomography) scan, that may require the use of drugs that can damage the kidneys.
Blood creatinine measurements, along with age, weight, and sex, are used to calculate the estimated glomerular filtration rate (eGFR), which is used as a screening test to look for evidence of early kidney damage.
Blood and urine creatinine levels may be used to calculate a creatinine clearance. This test measures how effectively the kidneys are filtering small molecules like creatinine out of the blood.
Increased creatinine levels in the blood suggest kidney disease or other conditions that affect kidney function including damage to or swelling of blood vessels in the kidneys, bacterial infection of the kidneys, prostate disease, kidney stone, or other causes of urinary tract obstruction etc.
Low blood levels of creatinine are not common, but they are also not usually a cause for concern. They can be seen with conditions that result in decreased muscle mass.
Creatinine blood levels can also increase temporarily as a result of muscle injury and are generally slightly lower during pregnancy.