Blood Urea Nitrogen (BUN)
Overview:
Levels of blood urea nitrogen (BUN) are determined using a simple blood test. High levels may indicate kidney disease (for example, infection of urinary tract obstruction), dehydration, gastrointestinal bleeding, some medications, or decreased kidney blood flow. Low levels may indicate liver disease, poor nutrition, or overhydration. BUN tests might be ordered with an annual checkup, especially if a patient has urinary problems or swollen ankles, which could indicate retention of fluid.
Detailed Information:
Urea is a substance that is formed in the liver when the body breaks down protein. Urea then circulates in the blood in the form of urea nitrogen. Urea then passes through the kidneys and is excreted. If the kidney is diseased in some way and unable to do its job, it may not properly process the urea, and BUN levels will elevate. Other possible causes of elevated BUN levels include:
- Kidney problems
- Congestive heart failure due to kidney problems
- Dehydration (because decreased fluid means there is not urine to excrete)
- Shock
- Heart attack
- Stress
- Hemorrhage into gastrointestinal tract
On the other hand, if liver function is impaired, then the liver will never form the urea in the first place, and BUN levels will be low. Other possible causes of low BUN levels include:
- Liver failure
- Malnutrition
- Overhydration
- Anabolic steroids
- Pregnant women normally have low BUN levels
Normal BUN levels vary depending on the person and the laboratory examining the sample. However, between 8 and 20 mg/100ml is a normal range.
For more information on blood tests in general, click here.
Last updated: 03-Jun-04
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