How Many Glasses of Water Should You Be Drinking Per Day? Myth vs. Science

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    Water is vitally important to our health and well-being. How much you need, though, depends on a variety of factors.

    How much water do you need per day?

    We all know how important water is. Without water, human beings can only survive for a matter of days. Drinking enough water to stay hydrated is essential not only for survival, but for our overall health. Water makes up about 60% of the body weight of adults, 75% of body weight in infants, and about 55% of body weight in the elderly.

    So, it’s clear that it’s important to drink water throughout the day. But how much? That depends on a number of factors, including body weight and biological sex. The Institute of Medicine recommends 2.7 liters (91 ounces) for women and 3.7 liters (125 ounces) for men. A good rule of thumb is to take your body weight and divide it by two; your result is how many ounces of water you should strive for per day. For example, if you weigh 150 pounds, you’ll ideally consume about 75 ounces of water daily.

    Factors that influence the amount of water you need


    Studies have shown that older people drink less water than younger people – and less water than they ought to drink, generally. The reason for this is simple: As people age, they get less thirsty. Even when older people are presented with a palatable selection of drinks, they’re still unlikely to drink enough water to replenish themselves.

    Young people, then, end up ingesting almost twice as much fluid daily than older people. Because older people tend not to drink enough water to replenish their body water deficit, it’s important to encourage regular fluid-ingesting habits, regardless of whether the person in question feels thirsty or not. If you’re getting older, in other words, get in the habit of drinking water even when you’re not thirsty. Your body needs it, and you’ll end up feeling better in the long run.


    The amount of water you need does depend to some degree on your weight. As mentioned above, a good rule of thumb is to take your body weight and divide it by two; your result is how many ounces of water you should strive for per day.

    Biological sex

    A recent study that tracked water intake among men and women between 2009 and 2012 showed that in general men ingest more water than women do. We also see a differentiation in the amount of “plain water” – as opposed to other liquids and foods – each group drinks as part of their daily fluid intake. Plain water represented 30% of the total water intake for men, while the remaining 70% was derived from other foods and liquids. Women actually drank more plain water than men did, with 34% of their total water intake coming from plain water, with the rest coming from other foods and liquids. Overall fluid intake was lower among men and women aged 60 and over, consistent with the tendency for older adults to be less thirsty than younger people.. In the same study, men and women both saw increases in water intake with increases in physical activity.

    As a reminder, the Institute of Medicine recommends 2.7 liters of water per day for women, and 3.7 liters of water per day for men.


    Your diet can play a big role in maintaining healthy water levels. There are many foods that are high in water content; including them in your diet will go a long way toward promoting your overall hydration. (More on this – and what types of foods – below.)

    Ways to hydrate besides drinking water

    There are many ways to hydrate besides drinking glasses of water – because water is present in all drinks and many foods. The following foods have a 90-99% water content:

    • Cantaloupe
    • Strawberries
    • Watermelon
    • Lettuce
    • Cabbage
    • Celery
    • Spinach
    • Pickles
    • Squash (cooked)

    So, if you’re looking to up your water intake but don’t want to chug cups of water all day, you should think about incorporating these food items into your diet. Fruits and vegetables in general are a healthy source of water. Fruit juice, yogurt, apples, grapes, oranges, carrots, cooked broccoli, pears, and pineapple all boast 80-89% water content.

    You may be surprised by what other food vitamins provide significant water content. You can have bananas, avocados, baked potatoes, and more (70-79% water content), or you can try pasta, ice cream, salmon, and chicken breast (60-69% water content). Options abound. Just try being intentional about what you’re deciding to eat and drink!

    In general, you shouldn’t rely on caffeinated beverages like coffee, tea, and certain sodas for your hydration, because the caffeine will make you urinate more – you’ll end up losing a lot of fluid this way. The same is true of alcoholic beverages: They may have high water content, but their diuretic properties make them a bad choice if your goal is greater hydration.

    Physical activity

    When engaging in physical activity, your body loses fluid, mainly through sweat. Therefore, as your physical activity increases, so will your need for ingesting more fluid to stay hydrated.

    Studies show that during athletic events, it’s normal for athletes to lose 6-10% of their body weight through sweat, thereby causing dehydration if fluids aren’t replenished. Even under low levels of dehydration, athletes engaged in intense physical activity will see their performance suffer, caused by reductions in endurace, increased levels of fatigue, declining motivation, and other key factors. During exercise, people often fail to adequately hydrate. As a result, dehydration can often last for some time after the physical activity has ended. If you’re staying physically active, be sure to drink water before, during, and after the activity.

    Children, in particular, are at a greater risk of dehydration, since they may not recognize the need to replenish their fluid intake. Child athletes should start their athletic activities in well-hydrated states and continue to drink fluids throughout. Responsibility falls to adults and coaches to make sure the children are getting the water they need.


    Studies show that physical performance in hotter environments leads to a greater risk of dehydration than performance in colder environments. Intense exertion in hot conditions without fluid replenishment can lead to hyperthermia, reduced blood flow to your muscles, and reduced cardiac output. Be mindful, too, of the humidity of your environment. The greater the humidity, the greater will be your need to rehydrate.

    Overall health

    Your water needs may vary based on the existence of certain health conditions. For example, congestive heart failure and kidney disease are conditions that can be adversely affected by drinking too much water. In other cases, though, you may need to up your fluid intake. Consult with a medical professional if you have concerns.

    Pregnancy and breast-feeding

    During pregnancy, your body needs more fluid than it usually would, in order to produce extra blood and amniotic fluid. Per the Institute of Medicine, pregnant people need to drink 10 eight-ounce glasses of water per day; while breastfeeding, that daily intake should go up to about 13 glasses per day.

    Health benefits of staying hydrated

    Water is an essential building block of cells in our bodies. Staying hydrated can support your overall health in a number of important ways, including: helping you maximize your physical performance; helping you maintain energy levels; promoting better cognition and overall brain health; helping prevent and treat headaches; promoting healthy digestion and alleviating symptoms of constipation; preventing and treating kidney stones; supporting weight loss efforts; and helping with those pesky hangovers.

    Can you drink too much water?

    Drinking too much water is technically possible, though it’s far from a common occurrence. Still, it’s good to be aware of a condition called “water intoxication,” which dilutes the body’s levels of sodium, potassium, and other important electrolytes. When your sodium levels fall too low, other health problems can emerge, including hyponatremia.

    Some pre-existing conditions that cause fluid retention in the body may make you more susceptible to water intoxication. These conditions are: congestive heart failure, poorly managed diabetes, and kidney disease.

    What is dehydration?

    Dehydration is the result of using more fluid than you take in. As a result, your body lacks the necessary water to carry out its regular functions.

    Symptoms of dehydration

    Some symptoms of dehydration include: dry mouth, dizziness, fatigue, dark urine, dry mouth, and more. It’s important to notice these symptoms and take action to address them. The health of your body relies on staying at the appropriate levels of hydration.

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    Dr. Carla Montrond Correia ND, CNS
    Medical Content Manager
    Dr. Montrond-Correia is a licensed naturopathic physician and a certified nutrition specialist (CNS). She holds degrees from University of Bridgeport, Georgetown University, and University of Saint Joseph, and supplemented her education with internships in the health and wellness space. She's focused on research, herbal medicine, nutrigenomics, and integrative and functional medicine. She makes time for exercise, artistic activities, and enjoying delicious food.
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