Good Question: How much water should we be drinking each day?

While most people have heard the advice to drink eight cups of water a day, there is some flexibility there and people are capable of drinking both too much and too little, though the latter is more common. 

Drinking too little can lead to dehydration which can cause a range of symptoms from dizziness to, in some extreme cases, death. Drinking too much also has potentially dangerous impacts because too much water in the body affects the body's electrolyte balance, experts said. They shared advice for how much a person should be drinking and the signs someone has had too much water -- and if the right balance exists for the average water drinker.  

How much water should you drink in a day?

While eight cups of water is a good rule of thumb when it comes to how much to drink, people also ingest fluids from the food they eat and from other beverages. About 20% of daily fluid intake usually comes from food. Between water, other drinks and food, adult men living in temperate climates need to ingest about 15.5 cups of fluids a day, according to the U.S. National Academies of Sciences, Engineering, and Medicine. Adult women living in temperate climates, one with average yearly temperatures that are not extreme, need to ingest about 11.5 cups of fluids a day. Women should drink more in a day if they're menstruating, pregnant or lactating.

The amount of water also varies depending on the climate and time of year. On a hot day, much of the fluids someone ingests are sweated out as the body tries to cool down. The average person has 2.6 million sweat glands and when a person sweats, they lose water and electrolytes. 

Drinking enough water and having enough electrolytes keeps the body functioning properly. Dehydration can cause dizziness, confusion, fatigue and extreme thirst. It can lead to more serious symptoms, such as heat exhaustion, heat stroke, seizures or kidney failure.

Can you drink too much?

Yes. The Centers for Disease Control and Prevention advises people not to drink more than 48 ounces, or six cups, per hour. Too much water or other fluids, such as sports drinks, can cause a medical emergency because the concentration of salt in the blood becomes too low. 

When this happens, the body's water levels rise and cells swell as your body tries to regulate the concentration of electrolytes, which can cause health problems, Dr. Mahesh Polavarapu, medical director of the emergency department at New York-Presbyterian Westchester, said.

"If you have too much water, it's going to basically push that water into cells to kind of balance out that sodium and other electrolyte concentrations," Polavarapu said. "So as that happens, your brain cells and other cells in your body start to swell." 

Drinking too much is not a common problem and the average, healthy adult should focus on hydration, health experts told CBS.

"This is not something you should be worrying about, you should be drinking as much water as you feel that's necessary," Polavarapu said.

Overhydration is seen more frequently in endurance athletes, people with kidney problems and those taking certain medications that can cause excessive thirst, such as antidepressants and diuretics, experts said. Older people are also more at risk because of age-related decline in overall organ function, which can increase someone's vulnerability to overhydration.

What are the signs you've had too much water?

This is where things can get tricky, Jason Ewoldt, a registered dietitian with the Mayo Clinic, said. Many of the symptoms of overhydration can be confused with the symptoms of dehydration. Both can cause nausea, muscle cramps and tiredness. There are some key ways to tell the difference.

"Being aware of thirst and urine color is the easiest way to limit the possibility of both overhydration and dehydration," Ewoldt said. 

If you're feeling thirsty, the chances are that you should be drinking more water. Dark yellow urine is also a sign to drink more. 

Clear urine is a sign that you may need to reel things in and drink less. 

What might happen if you drink too much water?

Too much water is associated with a condition called hyponatremia, which happens when the concentration of salt in the body is too low. It's also called "water intoxication." Drinking large quantities of water in a short period of time throws off the body's electrolyte balance. 

When someone over drinks, it's possible that their kidneys won't be able to keep up and excrete the excess water. 

"If you drink too much pure water, the solutes in your body have to distribute into additional space and you can get electrolyte disturbances that cause major problems in the brain and you can get seizures," Dr. David Metz, who's worked as a professor of medicine at the University of Pennsylvania's Perelman School of Medicine, said.

Other symptoms of hyponatremia can include nausea, vomiting, headaches, altered mental state/confusion, fainting, lethargy and coma. In some extreme cases, it can lead to death.

In a 2007 incident, 28-year-old Jennifer Strange, a mother of three from California, died of acute water intoxication after she participated in a water drinking contest. A radio station challenged participants to see who could drink the most water without using the restroom. At the time of the incident, one of Strange's co-workers said the victim "said to one of our supervisors that she was on her way home and her head was hurting her real bad... She was crying and that was the last that anyone had heard from her."

A 17-year-old football player died in 2014 in Georgia after he drank two gallons of water and two more gallons of Gatorade during practice. 

How should you safely drink water when it's hot out?

Drink before you feel thirst, the CDC recommends. If you're working outside in the heat, drink about 1 cup of water every 15 - 20 minutes. This translates to three-quarters to one quart (24-32 ounces,) an hour. Drinking more often is more effective for hydration than drinking large amounts infrequently. 

"People think about thirst as the thing that drives them to drink water, thirst is almost a later sign of dehydration, so don't try to wait for that to happen," Polavarapu said.

While drinking water is important to replace water lost via sweat, it's also important to eat regular meals to replace salt lost in sweat and maintain your electrolyte balance, according to the CDC.

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• Health

Aliza Chasan

Aliza Chasan is a digital producer at 60 Minutes and CBS News.

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