When you drink too much water, you may experience water poisoning, intoxication, or a disruption of brain function. This happens when there’s too much water in the cells (including brain cells), causing them to swell. When the cells in the brain swell they cause pressure in the brain. You may start experiencing things like confusion, drowsiness, and headaches. If this pressure increases it could cause conditions like hypertension (High Blood Pressure) and bradycardia (Low Heart Rate). Sodium is the electrolyte most affected by overhydration, leading to a condition called hyponatremia. Sodium is a crucial element that helps keep the balance of fluids in and out of cells. When its levels drop due to a high amount of water in the body, fluids get inside the cells. Then the cells swell, putting you at risk of having seizures, going into a coma, or even dying.