In older adults, dehydration is defined as loss of what?

• A. Loss of total body water
• B. Increased body fat
• C. Elevated blood glucose
• D. Reduced bone density

Answer: (A)

Dehydration is defined by a loss of total body water—a free-water deficit that raises plasma osmolality. In older adults, total body water is already lower and the thirst mechanism is blunted, so even small fluid losses can lead to dehydration. This definition focuses on fluid balance, whereas increases in body fat, high blood glucose, or reduced bone density describe other health issues and do not define dehydration.