How Much Water Do I Really Need to Drink?

Eight glasses a day is an OK place to start, but everyone’s fluid needs are different.

Drinking an adequate amount of water throughout the day can boost your physical and mental health, and is especially important for people managing chronic health conditions.

The amount of water you need for optimal health depends on various factors, and unfortunately, it’s not as simple as just drinking eight glasses a day. Here’s how to figure out your daily needs and why water is so important.

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How much water should I consume per day?

You may have grown up hearing that everyone should aim to drink 64 ounces (that’s 8 cups) of water every day. That advice has since been tossed aside, which makes sense — how could a 5-foot woman possibly need the same amount of water as a guy over 6 feet in his 20s?

The Institute of Medicine looked at U.S. survey data on water intake and concluded that this is the amount of water needed to prevent acute dehydration:

• 91 ounces or 11.5 cups per day for women
• 125 ounces or 15.5 cups per day for men

This is the only “official” guidance that exists, and that’s a pretty huge jump from 8 cups a day. Also, about 20% of your water intake comes from the food you eat, which makes it even more difficult to create a recommendation for how much water you should drink.

What factors impact how much water I need to drink?

Body size, age, and gender

Perhaps the most obvious factor in determining how much water you need is your body size. The larger your body, the higher your water needs will be each day.

Water makes up between 50% and 70% of your body weight (depending on your age), so larger people have more fluid in their bodies and higher fluid needs. Men have higher water needs than women and younger people have higher needs than older people.

Activity level

The more active you are, the more water you’ll need to drink. If you do intense exercise that leaves you sweaty, you’ll need to drink enough water to replace the water lost in sweat.

Environment

Being in warm or humid climates increases your water needs because you sweat more to cool off. Being at a higher altitude also increases your water needs.

Health status

Certain health conditions impact your water needs. For example, if you have kidney disease or congestive heart failure, you’ll need to work with your physician and a registered dietitian to determine your specific water needs each day.

It’s advisable to increase your water intake if you:

• are pregnant or nursing
• have a fever or are vomiting or have diarrhea
• are undergoing cancer treatment
• have diabetes or prediabetes

How does water intake impact my body, brain, and energy levels?

It’s pretty simple: If you’re not drinking enough water, you won’t feel your best.

Water is crucial for several bodily functions, including getting rid of waste (through urination, bowel movements, and sweat), regulating your body temperature, protecting your joints and sensitive tissues, and supporting the function of pretty much every cell in your body.

When you’re even slightly dehydrated, you’ll probably feel a little (or a lot) tired and cranky. According to research, inadequate water intake can have a negative effect on cognition, so you may have a harder time at work or school if you don’t drink enough.

How can I tell if I’m hydrated?

Some people find it helpful to track their water intake using a measured water bottle, tracking app, or something similar. But you don’t necessarily need these things to know if you’re drinking enough; your body has ways of telling you whether you’re hydrated or not.

If your pee is bright or dark yellow, you should drink more water. Pee that’s very dark amber can be a sign of serious dehydration — if yours is this color, you should seek medical attention.

Other signs you may need to drink more water are thirst, dry mouth, fatigue, dizziness or lightheadedness, headache, confusion, increased heart rate, muscle cramps, constipation, flushed skin, and swollen feet.

Is it possible to drink too much water?

Although rare, it is possible to overhydrate. Drinking too much fluid can lead to hyponatremia, which means your blood sodium levels are too low. In the short term, this can cause nausea, fatigue, and confusion.

If blood sodium levels are low for too long, it can lead to seizures and impaired heart function.

Hyponatremia happens most often in endurance athletes who lose both sodium and water through sweat, then drink too much water without also replacing sodium. Drinking an electrolyte drink after intense exercise can help prevent this.

Is it better not to drink water with meals?

If you’ve heard that it’s best not to drink while you eat, you can disregard this advice. Consistent water intake with and between meals throughout the day is the best way to stay hydrated and meet your goals.

How can I add more water to my diet?

If you need a little help upping your water intake, here are a few easy things to try.

Increase your fruit and vegetable intake

Eating more fluid-rich fruits and vegetables can help. Try snacking on watermelon or cantaloupe, or adding a side salad to lunch and dinner.

Buy a water bottle you love

Whether it’s a Nalgene, a Hydroflask, a Stanley Cup, or an Owala, investing in a water bottle you like will help you drink more during the day. I recommend a reusable tumbler with a straw to those who have difficulty with water intake since we tend to drink more when we use a straw.

Opt for water when dining out or drinking

When you eat out, always ask for a glass of water with your meal (even if you get another beverage). Servers often refill water glasses regularly, so you’ll probably drink more without even realizing it. And if you’re at a bar drinking alcohol, ask for at least one glass of water for every drink you consume

Add lime or a splash of juice for flavor

If plain water bores you, add a squeeze of lime or a splash of your favorite fruit juice. You can also opt for sparkling water, which is equally hydrating — just be aware that the bubbles can make you feel gassy.