Hyponatremia, common causes
Most common cause is excessive use of diuretics
Excessive sweating, diuretics (high ceiling), wound drainage, decreased secretion of aldosterone, hyperlipidemia, renal disease, NPO status, low salt diet.
Excessive hypotonic fluids
Psychogenic polydipsia, freshwater submersion accident, renal failure (nephrotic syndrome) irrigation with hypotonic fluids, syndrome of inappropriate antidiuretic hormone secretion, hyperglycemia, heart failure