What condition can cause elevated blood urea nitrogen (BUN) levels?

Elevated blood urea nitrogen (BUN) levels can indeed be caused by dehydration. This condition occurs when there is a deficit of fluid in the body, leading to a decreased volume of blood. When the body is dehydrated, the kidneys conserve water and concentrate urine, which results in a relative increase in BUN as nitrogen waste becomes more concentrated in the serum.

Moreover, during dehydration, the decrease in renal perfusion can lead to altered glomerular filtration rate (GFR), further contributing to elevated BUN levels. BUN is a waste product formed from the breakdown of protein, and when hydration status is low, the clearance of this waste product decreases, leading to higher concentrations in the blood.

Other conditions such as malnutrition, hypoglycemia, or excessive drinking do not directly cause an increase in BUN in the same manner that dehydration does. Malnutrition could potentially lead to altered BUN levels, but typically in a different context related to low protein intake; hypoglycemia is primarily a glucose-related state, and excessive drinking affects liver function and could lead to other metabolic derangements but does not typically elevate BUN on its own. Thus, dehydration is the most common and direct cause of elevated BUN levels in this context