Yes, you can drink too much water. Drinking a large amount in a short period can overwhelm the kidneys and dilute the sodium in the blood, causing a condition called hyponatremia, sometimes referred to as water intoxication.
When sodium levels become too low, water can move into the body’s cells and cause them to swell. Symptoms may include headache, nausea, vomiting, dizziness, muscle weakness or cramps, blurred vision, confusion, and hallucinations. Severe cases can cause breathing problems, seizures, coma, or even death.
Water intoxication can occur when someone drinks more than about 1 liter of water per hour. It may also occur in people doing intense exercise who drink large amounts of water without replacing the minerals they lose. The risk may be greater in people who already have kidney disease.
If water intoxication is suspected, immediate medical care is recommended because swelling in the brain can become life-threatening. Treatment may involve intravenous fluids to restore minerals such as sodium. A general practitioner can assess symptoms and determine whether further treatment is needed.