Which statement about albumin's role in fluid balance is correct?

• A. It draws fluid into vessels
• B. It keeps fluid within vessels
• C. It drains fluid from interstitial spaces
• D. It has no role in fluid balance

Answer: (B)

Albumin helps keep fluid inside blood vessels by generating colloid (oncotic) pressure in the plasma. This pressure pulls water from the surrounding interstitial space back into the capillaries, opposing the outflow caused by hydrostatic pressure. When albumin levels are low, the oncotic pressure decreases, fluid shifts into tissues, and edema can develop while circulating volume drops. Maintaining intravascular fluid relies on this albumin-driven pull, so describing its role as keeping fluid within vessels accurately reflects its function in fluid balance.