What is a common side effect of fever in patients?

Fever is a physiological response to infection or illness, where the body temperature rises above the normal range. One common side effect associated with fever is dehydration. As body temperature increases, the body may lose fluids through perspiration, increased respiration, and, in some cases, reduced intake of fluids due to decreased appetite or discomfort. This fluid loss can result in dehydration, which can lead to further complications if not adequately managed.

In contrast, enhanced appetite and increased energy are not typical responses during a fever; patients often experience a loss of appetite and fatigue. Improved cognitive function can also be negatively affected by fever due to the discomfort and potential impact on overall wellness, making dehydration the correct answer as it is a direct consequence of febrile states.