Drinking too much water can cause an imbalance in your electrolyte levels, but not usually because it washes them away. Rather, the problem is having too much water in your body. The resulting imbalance, commonly referred to as "water intoxication," is potentially fatal. Electrolytes are crucial for keeping your body’s fluid levels balanced, but your body also needs them for proper pH and for proper organ and muscle function.
Drinking too much water too fast also leads to an electrolyte imbalance because your kidneys cannot flush the water you consume quickly enough. This causes your blood to become waterlogged. This extra water then enters your cells, which swell. The issue becomes the lack of room for cells to expand in your brain. Swelling in your brain cells is dangerous because your brain is confined by your skull, thus cannot expand without causing symptoms. Rapid and severe cellular swelling can cause seizures, respiratory arrest, coma, brain stem herniation and even death, according to the June 2001 “Scientific American.”
You may suffer an electrolyte imbalance when the amount of a certain electrolyte you lose via urine or sweat is not properly replaced and you consume too much water. For example, you may have a blood-sodium level that falls too low, or hyponatremia. This may occur if you drink too much water during an event, such as a triathlon, because you lose sodium in your sweat. This dilutes the sodium content of your blood. When your sodium levels are too low, your body’s water levels can rise too high, causing your cells to swell.
Taking diuretics can “wash away” electrolytes, so to speak, because they cause you to excrete extra sodium in your urine. This raises your risk for hyponatremia. Other medications, dehydration, some recreational drugs, severe diarrhea or vomiting and numerous medical conditions also can raise your risk for low sodium levels that lead raise risk for hyponatermia.
Water intoxication has numerous symptoms. These include mental disorientation, headache, vomiting, nausea, fatigue and frequent urination. This condition usually is not caused by drinking too much water alone. It usually occurs when your body also secretes extra anti-diuretic hormone. This hormone causes your kidneys to conserve water. You secrete more of it during times of physical stress, such as a triathlon. Thus, your body may conserve water even if you are taking large amounts of it in. If you are an athlete, your best rule of thumb is to balance the amount of fluid you take in with the amount of sweat you produce – even if you are consuming sports drinks with electrolytes. Such drinks can lead to hyponatermia if you drink too much of them, according to “Scientific American.” Water intoxication is rare and most often associated in sports with ultra-endurance athletes, according to “Macroelements, Water and Electrolytes in Sports Nutrition,” by Judy Anne Driskell and Ira Wolinsky. In fact, mild hypnatermia is common among ultra-distance triathletes, though it’s usually not severe enough to produce symptoms, according to a 1999 “Medicine and Science in Sports and Exercise” study. In severe cases, fluid overload is the usual cause, notes lead study author D.B. Speedy.