Which symptom is NOT commonly associated with dehydration in aircrew?

• A. Thirst
• B. Dark urine
• C. Headache
• D. Increased alertness

Answer: (D)

Dehydration reduces circulating blood volume and can impair brain perfusion and function, so the body signals the need to drink and you may notice symptoms that reflect this strain. In aircrew, dry cabin air at altitude accelerates fluid loss, and the kidneys conserve water, leading to darker urine. Thirst is a common early cue, and a classic consequence is a headache from electrolyte shifts and reduced brain hydration. Dehydration also tends to lower alertness and performance, causing fatigue, slower reaction times, and difficulty concentrating. Increased alertness is not a typical sign; it would generally be unexpected as dehydration usually dulls cognitive function rather than enhances it.