What Is the Blood Urea Nitrogen Test?
A blood urea nitrogen test, frequently called a BUN test, is used to determine if the kidneys and liver are functioning appropriately. The test analyzes the level of nitrogen in the blood. Nitrogen is produced by urea, a product of chemical waste. Urea is made from broken down proteins in the liver. An individual with elevated blood urea nitrogen levels may have a malfunction of the kidneys, while lower levels may indicate a liver abnormality.
The kidneys are responsible for filtering urea from the body. Generally, urea leaves the liver and enters the kidneys where it is discarded from the body through urination. Kidneys that are working properly will filter out urea in an adequate manner. When there is a problem with the kidneys, urea will build up in the bloodstream. As a result, a blood urea nitrogen test will reflect an increase of nitrogen from the excessive urea.
In most cases, a blood urea nitrogen test is done if a doctor suspects an abnormality in the kidneys. The person may be exhibiting symptoms such as frequent urination, pain in the flanks, decreased urination or lower back pain. For people with kidney disease, a blood urea nitrogen test may be performed to detect the extent of kidney damage. It may also be done to see how well an established treatment is working. For instance, individuals on dialysis may frequently have this type of test to gauge the effectiveness of the treatments.
Commonly, blood creatinine levels may also be obtained during a blood urea nitrogen test. Creatinine, like urea, is a waste product. It is also generally filtered by healthy kidneys. For this reason, the presence of creatinine may additionally indicate a kidney problem. When both a blood urea nitrogen test and a creatinine test are done at the same time, the results will usually be compared for a bun-to-creatinine ratio.
A sample of blood will be collected for a blood urea nitrogen test. This type of test is usually considered painless, except for the minor prick of the needle. As with any injection site, there is a minimal risk of infection, although this does not happen often. After the blood is withdrawn, there may be some minor bruising. In the event that the injection site starts to rapidly bleed, an individual should apply pressure to the site and seek immediate medical care.
Patients are generally made aware of the results of a blood urea nitrogen test as soon as the doctor receives the results. High blood urea nitrogen levels may indicate a problem with the kidneys. The problem could range from an infection to an abnormal growth on the kidneys to a disease. There may be a problem with the liver if a test reveals particularly low levels. Doctors will typically treat the condition causing the abnormal levels, although, there are benign conditions that can cause blood urea nitrogen levels to become unbalanced in either direction.
Written by Nat Robinson
