It’s easy to believe that when it comes to hydration, more is always better.
We’ve all heard that the body is made mostly of water and that we should drink about eight glasses of water a day.
We’re told that drinking copious amounts of water can clear our skin, heal our colds, and aid in weight loss. And everyone seems to own a giant reusable water bottle these days, refilling constantly. So, shouldn’t we be chugging H2O at every opportunity?
Although getting enough water is very important for your overall health, it’s also possible (though uncommon) to consume too much.
Dehydration may always be in the spotlight, but overhydration also has some serious adverse health effects.
Here’s a look at what happens when you drink too much water, who’s at risk, and how to ensure you stay properly — but not overly — hydrated.
What is proper hydration?
Staying hydrated is important for bodily functions like blood pressure, heart rate, muscle performance, and cognition.
However, “proper hydration” is notoriously difficult to define. Fluid needs vary by age, sex, diet, activity level, and even the weather.
Health conditions like kidney disease and pregnancy can also alter the amount of water a person should drink each day. Certain medications can affect the body’s fluid balance, too. Even your own individual hydration needs can change from day to day.
In general, most experts recommend calculating half your weight and drinking that number of ounces per day. For example, a 150-pound person could strive for a daily total of 75 ounces (oz.), or 2.2 liters (L).
Adequate daily water intake by age
- Children ages 1 to 3: 1.3 L (44 oz.)
- Children ages 4 to 8: 1.7 L (57 oz.)
- Males ages 9 to 13: 2.4 L (81 oz.)
- Males ages 14 to 18: 3.3 L (112 oz.)
- Males ages 19 and older: 3.7 L (125 oz.)
- Females ages 9 to 13: 2.1 L (71 oz.)
- Females ages 14 to 18: 2.3 L (78 oz.)
- Females ages 19 and older: 2.7 L (91 oz.)
These target amounts include not only water and other fluids you drink, but water from food sources as well. A number of foods can provide liquids. Foods like soups and popsicles are recognizable sources, but less obvious items like fruits, vegetables, and dairy products also contain significant amounts of water.
So, you don’t need to only chug H2O to stay hydrated. In fact, other fluids can contain necessary nutrients you don’t get from regular water that are important for your health.
How much water can we handle?
While we all need plenty of water to maintain good health, the body has its limits. In rare cases, overloading on fluids can come with dangerous consequences.
So, how much is too much? There’s no hard number, since factors like age and preexisting health conditions can play a role, but there is a general limit.
“A normal person with normal kidneys can drink [roughly] as much as 17 liters of water (34 16-oz. bottles) if taken in slowly without changing their serum sodium,” says nephrologist Dr. John Maesaka.
“The kidneys will excrete all of the excess water fairly promptly,” Maesaka says. However, the general rule is that the kidneys can only excrete about 1 liter an hour. So the speed at which someone drinks water can also change the body’s tolerance for excess water.
If you drink too much too fast, or your kidneys don’t work properly, you may reach a state of overhydration sooner.
What happens when you drink too much water?
The body strives to constantly maintain a state of balance. One part of this is the ratio of fluid to electrolytes in the bloodstream.
We all need certain amounts of electrolytes like sodium, potassium, chloride, and magnesium in our bloodstream to keep our muscles contracting, nervous system functioning, and body’s acid-base levels in check.
When you drink too much water, it can disrupt this delicate ratio and throw off the balance — which is, unsurprisingly, not a good thing.
The electrolyte of most concern with overhydration is sodium. Too much fluid will dilute the amount of sodium in the bloodstream, leading to abnormally low levels, called hyponatremia.
Symptoms of hyponatremia may be mild at first, such as a feeling of nausea or bloating. Symptoms can become severe, especially when sodium levels suddenly drop. Serious symptoms include:
- unsteady gait
Hyponatremia vs. water intoxication
You may have heard the term “water intoxication” or “water poisoning,” but these aren’t the same thing as hyponatremia.
“Hyponatremia merely means the serum sodium is low, defined as less than 135 mEq/liter, but water intoxication means the patient is symptomatic from low sodium,” notes Maesaka.
Left untreated, water intoxication can lead to brain disturbances, since without sodium to regulate the balance of fluid within cells, the brain can swell to a dangerous degree. Depending on the level of swelling, water intoxication can result in coma or even death.
It’s rare and quite difficult to drink enough water to get to this point, but dying from drinking too much water is entirely possible.
Who’s at risk?
If you’re healthy, it’s unlikely that you’ll develop serious problems as a result of drinking too much water.
“Our kidneys do an excellent job at removing excess fluids from our body with the process of urination,” says dietitian Jen Hernandez, RDN, LD, who specializes in treating kidney disease.
If you’re drinking large amounts of water in an effort to stay hydrated, it’s more likely you’ll need frequent trips to the bathroom than a trip to the ER.
Still, certain groups of people have a higher risk for hyponatremia and water intoxication. One such group is people with kidney disease, since the kidneys regulate the balance of fluid and minerals.
“People with late-stage kidney disease can be at risk for overhydration, as their kidneys are unable to release the excessive water,” says Hernandez.
Overhydration can also occur in athletes, especially those participating in endurance events, such as marathons, or in hot weather.
“Athletes who train for several hours or outdoors are typically at higher risk of overhydration by not replacing electrolytes like potassium and sodium,” says Hernandez.
Athletes should be mindful that electrolytes lost through sweat can’t be replaced with water alone. An electrolyte replacement beverage may be a better choice than water during lengthy bouts of exercise.
Signs you may need to cut back
Initial signs of overhydration may be as simple as changes in your bathroom habits. If you find yourself needing to urinate so often that it disrupts your life, or if you have to go multiple times during the night, it may be time to reduce your intake.
Urine that’s completely colorless is another indicator you might be overdoing it.
Symptoms that indicate a more serious overhydration problem include those associated with hyponatremia, such as:
- loss of coordination
If you’re concerned, talk to your doctor. They can perform a blood test to check your serum sodium levels and recommend treatment if needed.
How to stay hydrated without overdoing it
It’s debatable whether there’s truth to the adage, “If you’re thirsty, you’re already dehydrated.” Still, it’s certainly a good idea to drink when you feel thirsty and to choose water as often as possible. Just make sure you pace yourself.
“Aim to sip water slowly throughout the day rather than waiting too long and downing an entire bottle or glass at once,” says Hernandez. Be especially careful after a long and sweaty workout. Even if your thirst feels unquenchable, resist the urge to chug bottle after bottle.
To hit the sweet spot for fluid intake, some people find it helpful to fill a bottle with their recommended adequate intake and drink it steadily throughout the day. This may be especially useful for those who struggle to drink enough, or simply to get a visual of an appropriate daily amount.
For many, however, it’s more practical to monitor the body for signs of adequate hydration than to focus on hitting a specific number of liters per day.
Signs you’re properly hydrated
- frequent (but not excessive) urination
- pale yellow urine
- ability to produce sweat
- normal skin elasticity (skin bounces back when pinched)
- feeling satiated, not thirsty
If you have kidney disease or another condition that affects your body’s ability to excrete excess water, it’s important to follow the fluid intake guidelines from your doctor. They can best assess your individual health and needs. You may be instructed to limit your water intake to prevent a dangerous electrolyte imbalance.
Additionally, if you’re an athlete — especially participating in endurance events like marathon running or long-range cycling — your hydration needs on race day look different than on a regular day.
“Having an individualized hydration plan in place prior to racing a longer event is important,” says sports medicine doctor John Martinez, MD, who serves as an onsite physician for Ironman triathlons.
“Know your relative sweat rates and how much you need to drink to maintain normal hydration. The best way is to measure body weight before and after exercise. The change in weight is a rough estimate about the amount of fluid lost in sweat, urine, and respiration. Each pound of weight loss is approximately 1 pint (16 ounces) of fluid loss.”
While it’s important to know your sweat rates, you don’t need to completely obsess over hydration while exercising.
“Current recommendations are to drink for thirst,” says Martinez. “You don’t need to drink at every aid station during a race if you are not thirsty.”
Be mindful, but don’t overthink it.
Finally, while it’s normal to be occasionally thirsty throughout the day (especially in hot weather), if you notice you feel the need to drink constantly, see your doctor. This may be a sign of an underlying condition that needs treatment.
Sarah Garone, NDTR, is a nutritionist, freelance health writer, and food blogger. She lives with her husband and three children in Mesa, Arizona. Find her sharing down-to-earth health and nutrition info and (mostly) healthy recipes at A Love Letter to Food.