Is it possible to drink too much water?

Originally Published: March 26, 1999 - Last Updated / Reviewed On: July 6, 2007
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Hi Alice,

I drink eight to ten 8-ounce glasses of water a day. Is it ever possible to drink too much water? A friend told me that it was possible and that drinking too much water sets your bodily fluids out of balance. Please let me know the details about water intake and health. Thanks.

Dear Reader,

More than half of our body is made up of water. Our bodies continuously send us signals to drink more water or excrete it in order to maintain homeostasis or internal fluid balance. As a result, a dry mouth or a feeling of thirst lets us know that we are dehydrated and need to replenish our fluids, whereas a feeling of fullness from drinking enough liquids is one of our bodies' ways of telling us to stop drinking. The average person requires a minimum of six to eight 8-ounce glasses of water per day to sustain a healthy environment in the body. It sounds like you're in the ballpark.

Water plays a vital role in maintaining a variety of body processes, such as:

  • Transportation of nutrients
  • Digestion
  • Maintenance of body temperature
  • Movement of metabolic wastes by means of sweat, urine, and feces
  • Lubrication of joints
  • Giving form to cells
  • Serving as a medium for thousands of chemical reactions in our bodies
  • Utilization of key nutrients
  • Helping the body's immune system
  • Reduction of fluid retention

For athletes and other active people, even more water is needed to replenish the water that is lost through perspiration. It is possible to sweat out more than two quarts of fluid per hour. It is generally recommended that for every pound of water lost during exercise (in sweat), an additional two cups of water need to be taken in.

It is possible, but rare in the United States, to consume too much water. Our kidneys are equipped to efficiently process fifteen liters of water a day. That's equivalent to drinking about sixty glasses of water! There is a rare condition called psychogenic polydipsia that causes consumption of an unhealthy amount of water. Abnormal thirst exhibited by people with this illness is based on a psychological disorder rather than on dehydration.

A condition as hyponatremia can also occur. This happens when your body has an increase in water levels, but your body's sodium levels stay the same. It can also happen if the body loses lots of sodium without losing a proportionate amount of water.  The excess water flows into your body's cells and causes them to expand.  Although most of the body's cells can handle this swelling, the brain cells cannot due to being enclosed in the hard, bony skull. Brain swelling is usually one of the most prominent signs of hyponatremia, along with loss of appetite, restlessness, fatigue, confusion, hallucinations and convulsions after drinking large amounts of water.  Usually, your body can handle large fluctuations in water-sodium balance when you drink a lot of water, but kidney problems, taking a diuretic, severe burns or stress due to surgery may put you at risk for this condition.  

Acute hyponatremia may occur in marathoners, so it is also important to drink sports drinks along with water during the race or other vigorous and prolonged athletic activity. Sports drinks contain sodium, among other electrolytes, that help keep everything in balance. If you are experiencing any of the symptoms described above, it is important that you consult with a medical professional immediately. Acute hyponatremia that occurs within 48 hours is considered more dangerous than non-acute, since its immediate onset means that there is more brain swelling. When the onset of hyponatremia is gradual, the brain cells have more time to adjust to the increased water levels and swelling is minimal in comparison.

Water-borne diseases are uncommon in countries with modern water-treatment systems. However if you rely on the tap for your water, be aware that the quality of tap water can vary significantly in certain areas of the world. When you are away from trustworthy sources, and unsure of the water quality, it is best to drink bottled water or boil your tap water to keep water-borne diseases and infections at bay. If clean water just isn't available, then bottled juice or soda may be your safest options for hydration.

Overall water is a great beverage choice because it quenches your thirst without sugars, artificial sweetners, or caffeine. As long as you have a source of clean, fresh water feel free to drink up!

Alice