Water poisoning, or water intoxication, typically occurs when a person drinks water faster than the kidneys can excrete it, leading to a dangerous dilution of sodium in the blood (hyponatremia). The kidneys can usually process about 1 liter (approximately 32 ounces) of water per hour. Consuming more than this amount over a short period increases the risk of water intoxication

. Symptoms of water intoxication can start to appear after drinking about 3 to 4 liters (roughly 1 gallon) of water within a few hours

. Drinking more than 1 liter per hour over several hours is generally considered risky and can lead to symptoms such as headache, nausea, confusion, muscle cramps, seizures, and in severe cases, coma or death

. In some documented cases, consuming around 6 liters in a short time has caused fatal water intoxication, such as in the tragic case of a water- drinking contest participant

. Chronic intake of 10 to 15 liters over several days can also cause intoxication in people with normal kidney function

. To summarize:

• Kidneys handle about 1 liter per hour safely.
• Drinking more than 3 to 4 liters within a few hours can cause symptoms.
• Drinking more than 1 liter per hour over several hours increases risk.
• Extreme cases involve 6 liters or more rapidly consumed, or 10–15 liters over days.

Preventing water intoxication involves drinking according to thirst, not forcing excessive intake, and balancing water with electrolytes especially during intense exercise

. Thus, water poisoning is caused by rapid consumption of water exceeding about 1 liter per hour, with symptoms starting around 3 to 4 liters in a short period and severe toxicity at higher amounts.