Alternative Names serum creatinine, serum creatinine level, creatinine level in the blood
Definition Creatinine is a waste product made by the body during regular metabolism. It is excreted into the urine by the kidneys. A serum creatinine test measures the level of creatinine in the blood.
The level of creatinine in the blood is a good measure of overall kidney function. When the kidneys are not working properly for any reason, they are not able to excrete creatinine into the urine. When this happens, the level of creatinine in the blood rises.
Who is a candidate for the test? This test is ordered for different reasons. For example, doctors may order this test when they think a person is dehydrated or has kidney damage. This test may also be ordered before or after a doctor prescribes certain medications. The main reason to order the test is to make sure the kidneys are working properly.
How is the test performed? To perform a serum creatinine test, a blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or "tourniquet," is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A fine needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle, and is collected in a syringe or vial. After the needle is withdrawn, the puncture site is covered with a bandage for a short time to prevent bleeding. The blood sample is sent to the laboratory to determine the amount of creatinine circulating in the blood.
What is involved in preparation for the test? Usually, no preparation is needed for this test. A person should request specific instructions from his or her health care doctor.
What do the test results mean? The normal level of creatinine varies slightly based on age, body size, and sex. The level also changes during Pregnancy. However, the normal level is usually between 0.04 and 0.12 mmol/L (millimoles per litre).
A decreased value for this test is rarely important. It can occur with decreased muscle mass, such as in elderly persons. Conditions such as muscular dystrophy, an inherited defect in muscles, can cause a low value for this test. pregnancy may also cause a low value.
An elevated value for this test can occur in many different situations, including:
decreased blood flow to the kidneys. This can occur with severe dehydration, massive blood loss, or congestive heart failure. Blockage in the kidney arteries, called renal artery stenosis, can also cause an elevated value on this test.
kidney damage or failure, which may be due to high blood pressure or diabetes. An inherited condition called polycystic kidney disease can also damage the kidneys. Damage to the kidneys can also occur when the blood calcium level is too high, called hypercalcaemia. A cancer called multiple myeloma is another cause. Autoimmune diseases, conditions in which a person's immune system attacks his or her own body, can also cause kidney damage.
taking certain medications, such as captopril or non-steroidal anti-inflammatory drugs, or NSAIDs
Other conditions can also cause an elevated value for this test. The meaning of the results should be discussed with the doctor.
Author: Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 17/11/2004 Contributors Potential conflict of interest information for reviewers available on request
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