The client is dehydrated.
The BUN test measures the amount of urea nitrogen in the blood. Urea, the major nitrogenous end-waste product of metabolism, is formed in the liver. The bloodstream carries urea from the liver to the kidneys for excretion. When the kidneys are diseased, they are unable to excrete urea adequately, and urea begins to accumulate in the blood, causing BUN to rise. Normal BUN is 8 to 25 mg/100 mL. Because other factors, such as high dietary intake of protein, fluid deficit, infection, gout, or excessive breakdown of protein stores, can also elevate BUN, it is not a highly sensitive indicator of impaired renal function.