What is the most common etiology of hyponatremia once you have ruled out medication and fluid overload?

Kidney disease: If you don't have too much water, and your salt intake is adequate (you only need 100 mg of sodium per day, average american diet is 3000-10, 000 mg per day), then evaluate the kidneys. Sounds like they are leaking sodium.

Too much water: You can drink too much water for a number of reasons. A specific hormone imbalance can interfere with thirst mechanism-this can be caused from a problem with the pituatary gland. Ecstasy and other drugs can cause hyponatremia.