However, there are many factors besides renal
disease that can cause BUN alterations, including
protein breakdown, hydration status, and
liver failure.
A decreased BUN may be seen in:
• Liver failure
• Malnutrition
• Anabolic steroid use
• Overhydration, Which can result from prolonged intravenous fluids
• Pregnancy (due to increased plasma volume)
• Impaired nutrient absorption
• Syndrome of inappropriate anti-diuretic secretion (SIADH) “
Taken from website http://www.rnceus.