To evaluate kidney function and monitor the effectiveness of dialysis
A blood sample taken from a vein in the arm
Urea is the final breakdown product of the amino acids found in proteins. Nitrogen in the form of ammonia is produced in the liver when protein is broken down. The nitrogen combines with other chemicals in the liver to form the waste product urea. The urea is released into the bloodstream and carried to the kidneys where it is filtered out of the blood and excreted in the urine. Healthy kidneys remove more than 90% of the urea the body produces, so blood levels can show how well your kidneys are working.
Most diseases that affect the kidneys or liver can affect the amount of urea present in the blood. If increased amounts of urea are produced by the liver or decreased amounts are removed by the kidneys then blood urea concentrations will rise. If significant liver damage or disease reduces the production of urea then urea concentrations may fall.
How is the sample collected for testing?
A blood sample is taken from a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is required.
How is it used?
When is it requested?
Urea may be used in a panel of tests:
- when someone has non-specific illness,
- as part of a routine group of tests, or
- to check how the kidneys are functioning before starting to take certain drugs.
Urea is often requested with creatinine:
- if kidney problems are suspected,
- to monitor treatment of kidney disease, or
- to monitor kidney function while someone is on certain drugs
- Tiredness, lack of concentration, poor appetite, poor sleep
- Swelling or puffiness (oedema) around the eyes, wrists, ankles or tummy
- Urine that is foamy, blood strained or coffee-coloured
- A decrease in the amount of urine
- Problems urinating such as a burning sensation, abnormal discharge during urination or a change in the frequency of urination especially at night
- Mid-back pain below the ribs where the kidneys are located
- High blood pressure
What does the test result mean?
High urea levels suggest poor kidney function. This may be due to acute or chronic kidney disease. However, there are many things besides kidney disease that can affect urea levels such as decreased blood flow to the kidneys as in congestive heart failure, shock, stress, recent heart attack or severe burns; bleeding from the gastrointestinal tract; conditions that cause obstruction of urine flow; or dehydration.
Low urea levels are not common and are not usually a cause for concern. They can be seen in severe liver disease or malnutrition but are not used to diagnose or monitor these conditions. Low urea levels are also seen in normal pregnancy.
Is there anything else I should know?
Urea levels increase with age and also with the amount of protein in your diet. High-protein diets may cause abnormally high urea levels. Very low-protein diets can cause abnormally low urea levels. Lower urea levels are also seen in infants and small children.
Drugs that damage kidney function may increase urea levels. Your urea and creatinine may be monitored if you are on certain drugs.
What other tests are used with urea to check how my kidneys are functioning?
How does urea change with age?
Urea levels increase with age. Urea levels in very young babies are about 2/3 of the levels found in healthy young adults, while levels in adults over 60 years of age are slightly higher than younger adults. Levels are also slightly higher in men than women.
What happens to urea in pregnancy?