Which lab value indicates that a patient may be dehydrated?

A BUN (Blood Urea Nitrogen) level of 25 mg/dL is significant in evaluating hydration status. Elevated BUN levels can suggest dehydration, as when the body is low on fluid, the kidneys retain water, leading to a higher concentration of urea in the blood. A BUN level above the normal range (which typically is around 7 to 20 mg/dL) serves as an indicator that the kidneys may not be effectively filtering blood due to limited blood flow resulting from dehydration.

In contrast, hemoglobin levels, while important for assessing overall health, do not specifically indicate hydration status. A normal hemoglobin level, such as 13 g/dL, does not provide evidence of dehydration. Similar reasoning applies to albumin and calcium levels. An albumin level of 4.0 g/dL is considered normal and does not reflect hydration status. Calcium levels, such as 9.0 mg/dL, typically fall within a normal range and do not provide relevant information regarding hydration either. Thus, elevated BUN is the most telling lab value indicating that a patient may be dehydrated.