A creatinine blood test measures the level of creatinine in the blood. Creatinine is a waste product that forms when creatine breaks down. Creatine is a substance found in muscle. Creatinine levels help determine how well your kidneys function. Your kidneys are responsible for eliminating creatinine from the body when you urinate. When creatinine levels increase, your kidney function may be impaired.
Creatinine levels are usually performed along with several other laboratory tests, including BUN (blood urea nitrogen) and a basic or comprehensive metabolic panel (BMP or CMP). These tests are performed during routine physical exams to help diagnose a number of diseases like diabetes, and to look for any problems with how your kidneys are functioning.
Your doctor might order a blood test to assess your creatinine levels if you show signs of kidney disease:
- fatigue and trouble sleeping
- loss of appetite
- swelling in the face, wrists, ankles, or abdomen
- lower back pain near the kidneys
- changes in urine output and frequency
- increase in blood pressure
Kidney problems can be related to a number of different diseases or conditions, including:
- glomerulonephritis: damage to the filtering capacity of the kidneys
- pyelonephritis: bacterial infection of the kidneys
- death of kidney cells caused by drugs or toxins
- prostate disease or blockage of the urinary tract (for instance, blockage caused by kidney stones)
- decreased blood flow to the kidneys due to dehydration, atherosclerosis, shock, congestive heart failure, or diabetes
Aminoglycoside medications (e.g. gentamycin) can cause damage to the kidneys in some people. If you are taking this type of medicine, your doctor may order regular creatinine blood tests to make sure your kidneys are healthy.
Some medications can increase your creatinine levels without causing kidney damage. Let your doctor know if you take:
- NSAID medications like aspirin or ibuprofen
- chemotherapy drugs
You may be asked to stop taking your medication before the test. Or, your doctor may just note the drug interaction in your files.
Other than that, you don’t have to do much to prepare—the test is just a standard blood draw.
Creatinine testing requires a simple blood draw at your local lab facility. You will be asked to pull up your sleeves so the technician can find a visible vein. Most often a vein on the inside of your elbow is used. The technician, called a phlebotomist, inserts a needle into your vein to collect the blood. Creatinine blood tests do not hurt, but you might feel a slight prick when the needle is inserted. After the technician removes the needle, they will put a bandage on the site of the blood draw.
Your doctor will notify you of the results within a few days of testing.
Creatinine is measured in milligrams per deciliter of blood (mg/dL). People who are more muscular tend to have higher creatinine levels.
Normal creatinine levels range from 0.7 to 1.3 mg/dL in men and 0.6 to 1.1 mg/dL in women.
Increased creatinine levels in the blood are indicators that the kidneys may not be functioning properly.