It’s never been trendier or easier to hydrate thanks to a massive wave of reusable water bottles on the market. But while you’re likely aware that you should be well-hydrated, it’s fair to wonder just what that means. How much water should you drink a day? And is the amount the same for everyone?
While there are clear hydration numbers out there to strive for, doctors and nutritionists say the right amount of water to try to drink daily is a little different for everyone. In fact, it can even vary for you based on what you do in any given day.
Meet the experts: Eric Adkins, M.D., is an emergency medicine physician at the Ohio State University Wexner Medical Center; Devon Wagner, R.D.,a nutritionist at The Ohio State University Wexner Medical Center; Stephani Johnson, D.C.N., R.D.N., is an adjunct professor in the Department of Clinical and Preventive Nutrition Sciences at Rutgers University; Christy Brissette, R.D., owner of 80 Twenty Nutrition.
Here’s what the recommendations say, plus why your individual hydration goals may be a little different.
How much water should you drink a day?
The U.S. National Academies of Sciences, Engineering, and Medicine has very clear guidelines on how much water to drink a day.
According to the organization, women should aim to have 11.5 cups (92 ounces) of fluids a day, while men should have 15.5 cups (124 ounces) of fluids a day. It’s important to point out that those fluids come from food and drink—and about 20% of your daily fluid intake usually comes from foods.
“However, many things can impact fluid needs,” says Stephani Johnson, D.C.N., R.D.N., an adjunct professor in the Department of Clinical and Preventive Nutrition Sciences at Rutgers University. Meaning, you could be over- or under-hydrating if you just follow these guidelines and don’t pay attention to your body’s cues about hydration.
What about the advice to drink 8 glasses a day?
There are a few potential issues with the advice to drink eight glasses of water a day. One is that there’s so much variability in glass size. “Eight glasses may be enough, but it depends on the size of the ‘glass’ and individualized needs,” Johnson says. Meaning, you’re going to be taking in wildly different amounts if you're using 8-oz glasses vs. 16-oz glasses as your measurement. Advice to drink eight glasses a day isn’t wrong—it’s just not very precise.
If you use a cup as your measurement, you’re then looking at 8 oz per glass. If you aim to have eight of those glasses, you’re only at 64 oz of water a day. That’s well under the recommended 92 oz of water a day for women and 124 oz a day for men.
Still, if you aren’t currently drinking enough water at the moment and need an easy guide to follow, Johnson says aiming to have eight glasses of water a day is a good starting point.
Factors that influence how much water you need
Breaking hydration goals down by sex is one way to look at it, but the reality of what you actually need is much more complex. Johnson says that these factors can influence how much water you need:
- Sex: Men usually—but not always—require more fluids than women because they tend to have greater muscle mass, which holds more water.
- Sweat: You lose fluids when you sweat, and the amount of fluid loss is based on your climate, temperature, and physical activity level. “The more you sweat, the more water you need,” Johnson points out.
- Age: Your total body water content decreases as you get older, your sense of thirst sensation drops, and your kidney function becomes less efficient. That tends to increase your hydration needs with age.
- Body size: People who are bigger lose more water because they have a larger skin surface area. They also require more fluids for overall bodily functions. “To get a rough idea of how much water you need, divide your weight in pounds in half,” says Christy Brissette, R.D., owner of 80 Twenty Nutrition. “That's how many ounces of water you should aim to drink per day.”
- Diet: You may need less fluids if you eat foods with a high water content, like melons, cucumbers, or soups. But loading up on high-fiber foods may mean you need to drink more. “Eating a high fiber diet also increases your fluid needs because fiber absorbs water,” Brissette says.
- Alcohol: Alcohol is a diuretic, which means it makes you pee more. It ultimately increases your hydration needs.
- Medical conditions: Some conditions, like those that cause diarrhea, will raise your fluid needs. Others, like congestive heart failure, may reduce them.
- Breastfeeding and pregnancy: Nursing moms have higher fluid needs, which can vary based on how much milk they produce. Pregnant people also need more fluids than others, Brissette says.
Why hydration is important
Your body is made up of about 55%-60% water. With that, it’s important to stay well hydrated for everything to function properly in your body, says Devon Wagner, R.D.,a nutritionist at The Ohio State University Wexner Medical Center.
“Digestive function, skin health, kidney function, and regulating body temperature all require adequate fluid intake,” Wagner says.
Water is also required for your body to move nutrients around and to flush out waste, Brissette says. Being well hydrated protects your organs and tissues, lubricates your joints and the spinal column, and plays a “vital role” in supporting brain function, Wagner says.
“Without sufficient water intake, many bodily processes become impaired, with the severity of health consequences depending on the degree of dehydration,” she says. “Adequate hydration is essential, but there are negative health outcomes associated with over-hydration, so more is not always better.”
Can drinking a lot of water help you lose weight?
Drinking water may help you lose weight, but it’s not a given. “Thirst is sometimes mistaken for hunger, so having a glass of water before eating can be a helpful way to pause and determine whether you're actually hungry,” Brissette says.
Being dehydrated can also cause what Wagner calls “pseudo-cravings,” especially for things that are salty or sweet. As a result, doing your best to have enough water in your day may help lower the odds you’ll deal with urges to eat less healthy foods.
If drinking more water is the only thing you do for weight loss, Brissette says you're unlikely to see a significant change. But if you're hydrating well, being active, and focusing on good nutrition, it can help support your weight loss goals.
Do drinks other than water help with hydration?
While nutritionists agree that water is your best bet for hydration, it’s not the only option. Wagner suggests looking for drinks that are very low calorie, like herbal tea, making sure to limit caffeine. “Caffeine pulls fluid out of our bodies and can increase our risk of dehydration if drinking in excessive amounts,” she says.
If you’re sweating a lot, it’s OK to reach for something with electrolytes, like a sports drink, says Eric Adkins, M.D., is an emergency medicine physician at the Ohio State University Wexner Medical Center. (This just shouldn’t be the only thing you drink.) “Coconut water is an acquired taste, but it can help when you put a hard workout in and are feeling depleted,” he says.
Again, certain foods can help with hydration, too, like cucumbers, watermelon, tomatoes, celery, oranges, and zucchini.
How to tell if you’re well hydrated
Keeping tabs on how much water you drink in a day can help you stay on track. But Dr. Adkins points out that it’s best to listen to your body. “Everyone asks how much water they should be drinking, but a lot depends on your environmental circumstances and your own body,” he says.
That’s why he generally recommends paying close attention to the color of your urine. “If it looks dark orange or a darker yellow, it’s an indication that you’re not getting enough water,” Dr. Adkins says. On the other side, he says you may be overdoing it if it constantly looks like you’re urinating out water. One caveat, per Brissette: If you’re taking a multivitamin or B vitamins (especially riboflavin), your pee might look bright yellow regardless of how much you drink. “That’s completely normal and a sign that your body is getting rid of any extra riboflavin it doesn’t need,” she says.
Again, the amount of water you should drink a day is a little variable. But paying close attention to what lands in the toilet bowl and making adjustments based on that can go a long way toward making sure you’re well-hydrated.
