What can occur if fluid intake exceeds output?

When fluid intake exceeds output, one of the primary consequences is weight gain. This occurs because the excess fluid accumulates in the body's tissues, leading to an increase in total body water. This is often seen in conditions like heart failure, renal insufficiency, or excessive fluid administration, where the kidneys cannot excrete the excess fluid, resulting in edema or an increase in extracellular fluid volume.

While other options relate to potential complications of fluid imbalance, they are not as directly tied to the immediate outcome of excess fluid intake. Weight gain is a clear and direct result that can be easily observed and measured, making it the most fitting answer in this context. Understanding fluid balance is essential for monitoring patients, especially those with conditions that predispose them to fluid overload.