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).
The creatinine blood test measures the level of creatinine in the blood. This test is done to see how well your kidneys work.
Creatinine can also be measured with a urine test.
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.
Purpose of a Creatinine Blood Test
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.
Preparing for a Creatinine Blood Test
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 Blood Test Procedure
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.
Understanding Your Results: Normal Creatinine Levels
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.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging sensation. Afterward, there may be some throbbing or slight bruising. These soon go away.
Why the Test is Performed
Creatinine is a chemical waste product of creatine. Creatine is a chemical made by the body and is used to supply energy mainly to muscles.
This test is done to see how well your kidneys work. Creatinine is removed from the body entirely by the kidneys. If kidney function is not normal, creatinine level increases in your blood. This is because less creatinine is released through your urine.
The creatinine level also varies according to a person’s size and muscle mass.
A normal result is 0.7 to 1.3 mg/dL for men and 0.6 to 1.1 mg/dL for women.
Women usually have a lower creatinine level than men. This is because women usually have less muscle mass than men.
The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Is there anything else I should know?
Some drugs may cause increased creatinine levels. Inform your health care provider of any drugs you are taking.