Creatinine blood test
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.
How the Test is Performed
A blood sample is needed.
How to Prepare for the Test
The health care provider may tell you to temporarily stop taking certain medicines that can affect the test. Medicines include:
- Aminoglycosides (for example, gentamicin)
- Heavy metal chemotherapy drugs (for example, cisplatin)
- Kidney damaging drugs such as cephalosporins (for example, cephalexin)
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
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.
What Abnormal Results Mean
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 pregancy, such as seizures (eclampsia), or high blood pressure caused by pregnancy (preeclampsia)
Lower than normal level may be due to:
- Conditions involving the muscles and the nerves that control them (myasthenia gravis)
- Muscle problems, such as late stage muscle loss (muscular dystrophy)
There are many other conditions for which the test may be ordered, such as high blood pressure, diabetes or medication overdose. Your health care provider will tell you more, if needed.
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)
Israni AK, Kasiske BL. Laboratory assessment of kidney disease: filtration rate, urinalysis, and proteinuria. In: Taal MW, Chertow GM, Marsden PA, et al., eds. Brenner and Rector’s The Kidney. 9th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 25.
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.