Increased BUN levels suggest impaired kidney function. This may be due to acute or chronickidney disease, damage, or failure. It may also be due to a condition that results in decreased blood flow to the kidneys, such as congestive heart failure, shock, stress, recent heart attack, or severe burns, to conditions that cause obstruction of urine flow, or to dehydration.
BUN concentrations may be elevated when there is excessive protein breakdown (catabolism), significantly increased protein in the diet, or gastrointestinal bleeding (because of the proteins present in the blood).
Low BUN levels are not common and are not usually a cause for concern. They may be seen in severe liver disease, malnutrition, and sometimes when a person is overhydrated (too much fluid volume), but the BUN test is not usually used to diagnose or monitor these conditions.
Both decreased and increased BUN concentrations may be seen during a normal pregnancy.
If one kidney is fully functional, BUN concentrations may be normal even when significant dysfunction is present in the other kidney.
This article was last reviewed on November 29, 2012. | This article was last modified on February 24, 2015.
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