The creatinine blood test measures the level of creatinine in the blood. This test is done to see how well your kidneys are working.
Creatinine can also be measured with a urine test.
How the Test is Performed
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. This soon goes away.
How to Prepare for the Test
The health care provider may tell you to temporarily stop taking certain medicines that can affect the test. These medicines include:
- Cimetidine, famotidine, and ranitidine
- Certain antibiotics, such as trimethoprim
Tell your provider about all the medicines you take.
A normal result is 0.7 to 1.3 mg/dL (61.9 to 114.9 µmol/L) for men and 0.6 to 1.1 mg/dL (53 to 97.2 µmol/L) for women.
Women usually have a lower creatinine level than men. This is because women usually have less muscle mass than men. Creatinine level varies based on a person's size and muscle mass.
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 person 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 lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
What Abnormal Results Mean
A higher than normal level may be due to:
- Blocked urinary tract
- Kidney problems, such as kidney damage or failure, infection, or reduced blood flow
- Loss of body fluid (dehydration)
- Muscle problems, such as breakdown of muscle fibers (rhabdomyolysis)
- Problems during pregnancy, such as seizures caused by eclampsia or high blood pressure caused by preeclampsia
A lower than normal level may be due to:
- Conditions involving the muscles and nerves that lead to decreased muscle mass
There are many other conditions for which the test may be ordered, such as high blood pressure, diabetes, or medicine overdose. Your provider will tell you more, if needed.
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, the creatinine level in your blood will increase. This is because less creatinine is released through your urine.
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Inker LA, Fan L, Levey AS. Assessment of renal function. In: Johnson RJ, Feehally J, Floege J, eds. Comprehensive Clinical Nephrology. 5th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 3.
Landry DW, Bazari H. Approach to the patient with renal disease. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 114.