Which is a cause of hyponatremia?

• A. Fluid overload
• B. Hyperkalemia
• C. Edema
• D. Dehydration

Answer: (A)

Hyponatremia arises when there is more water relative to sodium in the body, causing the serum sodium concentration to drop due to dilution. Fluid overload directly leads to this dilutional state because excess free water lowers the sodium concentration in the blood. In conditions of fluid overload, the body may retain water or fail to excrete it properly, driving the dilution of serum sodium. The other options don’t fit as well: dehydration lowers total body water and tends to raise sodium (hypernatremia), hyperkalemia is about potassium balance and does not inherently reduce sodium, and edema signals excess fluid but isn’t the direct mechanism by itself for low sodium.