Definition This test determines the level of urea nitrogen in the blood.
Urea is produced when proteins are metabolised or broken down. Elevated levels of serum urea can be a sign of kidney disease, liver disease or dehydration.
Who is a candidate for the test? This test is normally done to evaluate kidney function and aid in diagnosing kidney disease. It may also be performed to assess for dehydration.
How is the test performed? In order to measure the serum urea levels in the blood, 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 to enlarge 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 for testing in the laboratory. After the needle is withdrawn; the puncture site is covered for a short time to prevent bleeding.
What is involved in preparation for the test? A person should request specific instructions from his or her doctor.
What do the test results mean? Normal values for Urea are 2.5 - 7.9 mmol/L (millimoles per litre) of blood.
Author: David T. Moran, MD Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 6/06/2005 Contributors Potential conflict of interest information for reviewers available on request
