Urea is formed by the liver when protein is metabolised into amino acids. This test measures the amount of urea in the blood.
Urea is released by the liver into the blood and is carried to the kidneys where it is filtered out of the blood and released into the urine as a waste product. The process is ongoing, thus there will always be a small amount of Urea in the blood.
Diseases that affect the kidneys or liver can affect the amount of urea in the blood. Levels will increase when increased amounts are produced by the liver or the kidneys are not functioning properly to filter waste products out of the blood. Levels will be very low in sever liver damage where there is limited Urea production.
Urea tests are used with Creatinine tests to evaluate kidney function, to help diagnose kidney disease and to monitor people with acute or chronic kidney dysfunction or failure who are on treatment like kidney dialysis. It may be used to evaluate a person's general health status.
Urea tests are commonly ordered for the following reasons: