Dehydration primarily involves loss of fluid from which compartment?

• A. Intracellular fluid
• B. Extracellular fluid
• C. Plasma
• D. Interstitial fluid

Answer: (A)

Dehydration is a deficit of total body water that raises the osmolality of the extracellular fluid. When the extracellular fluid becomes hyperosmolar, water moves out of cells to restore balance, causing the intracellular fluid to shrink. So, the compartment that loses water most directly is the intracellular fluid, leading to intracellular dehydration. The extracellular fluid compartments (plasma and interstitial) are affected as water is lost from the body, but the immediate, defining change is the depletion of water from inside the cells.