It’s hard believing drinking too much water can kill you and can be considered a poison when over-consumed within a specific period of time.

Water intoxication occurs when a person drinks excessive quantities of water without adequate electrolyte intake. The real danger from water poisoning, more politely called water intoxication, isn't that a person drinks far too much water.

The real danger, which can be life-threatening, is that too much water in a human body can dilute the sodium (or salt) the body absolutely needs for normal nerve and muscle function.

Low sodium level in blood, whose clinical name is "hyponatremia," prevents this essential electrolyte from keeping our bodies' fluids in a normal balance. Water intoxication or overhydration results when the normal balance of electrolytes in the body is pushed outside safe limits by excessive water intake.

What exactly does sodium do for us? Sodium is one of the body's electrolytes, which are minerals the body needs in quite large amounts to keep functioning. Electrolytes carry an electric charge when dissolved in body fluids such as blood.

Most of our body’s sodium is located in our blood and in the fluid around cells.

Our bodies obtain sodium through food and drink then lose it mostly in sweat and urine. Healthy kidneys maintain a consistent level of sodium in the body by adjusting the amount excreted in urine. When sodium consumption and loss are not in balance, the total amount of sodium in the body is affected.

The total amount of sodium in the body is important because it affects the amount of fluid in blood (or blood volume) and around cells. Our body continually monitors blood volume and sodium concentration.

When either becomes too high, sensors in the heart, blood vessels, and kidneys detect the increase and stimulate the kidneys to increase sodium excretion, thereby returning blood volume to normal.

On the other hand, when blood volume or sodium concentration becomes too low, sensors trigger mechanisms to increase blood volume.

Remember water intoxication won’t likely occur unless a person drinks a large volume of water within a short period of time (within one or two hours, for example). Water intoxication can be prevented if a person’s intake of water doesn’t grossly exceed their water losses via urine or sweat.

How much water is too much to drink within a short period of time?

When someone has normal and healthy kidneys they should be able to excrete about 800 milliliters to 1 liter of fluid each hour. That’s equal to about 3.3 to 4.2 cups or 0.21 to 0.26 gallons per hour.

Drinking more than this amount will cause an imbalance of electrolytes. It will also likely show some early symptoms associated with hyponatremia such as headaches, confusion, disorientation, nausea and vomiting.

People who exercise hard are in particular danger from hyponatremia because their tendency will be to drink too much water to compensate for their water lost as sweat. Their bodies will also accumulate even more water because their bodies are experiencing a stress response.

The normal serum sodium concentration reference range is about 132 to 144 mmol/liter. Developing dangerously low sodium levels due to water flushing too much sodium from the body can cause serum sodium concentration fall to below 110 to 120 mmol/liter.

In severe cases, sodium might even fall to 90 to 105 mmol/liter. Serum concentrations this low can cause a number of serious symptoms and can potentially be deadly.

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