Fluid deficit that triggers thirst

Remote Pilot (Part 107) practice question 7 of 20 on Operations / Physiology. ACS element UA.V.E.K1 · difficulty: recall. Want to answer it in a timed quiz? Use the Remote Pilot (Part 107) practice mode.

Question bank updated 2026-09-22

QUESTIONAccording to the Remote Pilot Study Guide, most people become thirsty after what level of fluid loss?

AA 0.5-quart deficit, or 1 percent of body weight
BA 1.5-quart deficit, or 2 percent of body weight
CA 3-quart deficit, or about 10 percent of body weight

Show the answer and explanation

Correct answer: B. A 1.5-quart deficit, or 2 percent of body weight

A — incorrect These figures are smaller than those in the study guide; thirst is triggered at a 1.5-quart deficit or a 2 percent loss of body weight.
B — correct The study guide states that most people become thirsty with a 1.5-quart deficit or a loss of 2 percent of total body weight, the point at which the thirst mechanism is triggered.
C — incorrect These figures are far larger than the study guide's; thirst appears at a 1.5-quart deficit, well before such a loss.

BACKGROUND

The Remote Pilot Study Guide says the key for pilots is to be continually aware of their hydration. Most people become thirsty with a 1.5-quart deficit or a loss of 2 percent of total body weight, which triggers the thirst mechanism. The problem is that this mechanism arrives too late and is turned off too easily: a small amount of fluid in the mouth shuts it off, delaying replacement of the needed fluid. Pilots are advised to stay ahead of thirst rather than relying on it as an alarm, and to carry a container to measure daily intake.

STUDY TIP

Remember the pair 1.5 quarts / 2 percent and the lesson that thirst is a late, unreliable warning.

KEY POINTS

Thirst is triggered at a 1.5-quart deficit or 2 percent of body weight.
The thirst mechanism arrives too late and is turned off too easily.
Stay ahead of thirst; do not use it as an alarm.

SOURCES

remote_pilot_study_guide.txt ch9 "Dehydration"

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