Which is a risk factor for fluid volume excess (FVE)?

• A. Excess sodium intake
• B. Excess fluid intake
• C. Dehydration
• D. Regular physical activity

Answer: (A)

Excess sodium intake is a primary driver of fluid volume excess because sodium is the main extracellular cation and governs osmolality. When sodium intake is high, the kidneys may retain more sodium, and water follows to balance the osmotic pressure. This increases extracellular fluid volume—both in the bloodstream and interstitial spaces—leading to edema and typical signs of fluid overload. So, even if fluid intake is normal, too much sodium can push the body toward retaining water and expanding volume.

Excess fluid intake can contribute in some situations, but the body’s control of water is tightly linked to sodium balance, making sodium the more direct and modifiable risk factor. Dehydration reduces total body fluid, not increases it, and regular physical activity generally supports better fluid balance rather than causing excess.