Drinking too much water can be dangerous and has proven fatal. This may come as a surprise to dieters or athletes who are told to make sure they get adequate fluids. The condition caused by drinking too much water is called water intoxication. It can have several possible effects, which can quickly cause an emergency medical situation.
While most people are safe to drink six to eight glasses of water a day, dieters or athletes can try to get an extra edge by drinking more. Especially high-performance athletes, such as marathon runners, can drink excessively. This can cause an imbalance of the body's electrolytes. Too much water can quickly deplete electrolytes like sodium compounds.
Rapid intake of too much water floods the interior of cells when sodium is depleted. This sodium depletion, called hyponatremia, can rupture cells, either from additional pressure on the cells from outside or from pressure inside the flooded cells. As cells break down in various parts of the body, certain symptoms quickly emerge. Severe vomiting and nausea are common. Headache can occur as the brain swells. A person may be confused or disoriented.
Symptoms progress and may include seizures and coma. Untreated cases can and have resulted in death. The hazing incident in Chico, California that caused the death of Michael Carrington in 2005 was the direct result of drinking too much water. Additionally, Carrington was forced to perform exercises in a very cold basement. His death was noted as heart failure from water intoxication.
Runners have also collapsed from drinking too much water quickly. Some sports drinks replace electrolytes as they replace fluids. However, not all beverages marketed as "sports drinks" are equivalent. In general, a doctor will be able to tell you what the best drinks are when you are competing in sports. Additionally, runners are now advised to drink when thirsty, rather than anticipate thirst. This helps reduce fluid intake to the amounts needed in many cases, although most electrolyte replacement drinks are still better options than water, which may be consumed in excessive amounts to satisfy thirst.
Too much water is generally defined as water consumed in excess of what the kidneys can process in an hour. Extremely healthy kidneys could process about 30 ounces (about .9 liters) of water in an hour. A person with kidney problems or with only one kidney should drink much less, depending on the doctor's instructions.
The person with healthy kidneys could develop water intoxication by drinking about 2 to 3 times what the kidneys can process. For a person with kidney problems or one kidney, excess water might be defined as just an ounce or two over the recommended amounts.
For people with healthy kidneys, it should be perfectly safe to drink two cups of water per hour, and for the dieter, even one cup per hour will qualify for plenty of water. However, drinking too much water in quick succession can prove fatal and should definitely be avoided.