To survive and thrive, we all need water. It protects our organs, ensures nutrients are delivered to cells, and even regulates our body temperature — just to name a few functions! So how do you know if you're hydrated, and how much water does your body actually need? You might be surprised.

By Marge Perry
Each product we feature has been independently selected and reviewed by our editorial team. If you make a purchase using the links included, we may earn commission.
woman drinking water from a sports bottle
Credit: Peopleimages/Getty Images

Eight a Day?

You've probably heard you should drink eight 8-oz. glasses of water a day. While easy to remember, that's a little misleading. Humans are different sizes and shapes, have different metabolisms, live in a variety of climates, and have varied diets — all of which affect how much water we need.

The National Academy of Medicine (NAM) recommends women consume about 91 ounces and men about 125 ounces of water daily — from all sources. That includes water we get from food, which is estimated to be roughly 20 percent of our total water consumption. (A diet high in "wet" foods, such as cucumbers, celery, lettuce, tomatoes, and watermelon, has a higher percentage of water.) It also includes water from other beverages: tea or coffee, milk for your cereal, a bowl of soup, and even a glass of wine. So you might actually need only four big glasses of water. You'll know you need to drink up if you experience dry mouth, irritability, fatigue, and headaches — all symptoms of mild dehydration.

We can survive without water for three to seven days. But even being slightly dehydrated can wreak havoc. Proper hydration keeps your joints lubricated, helps prevent infections, maintains a healthy metabolism, and helps your heart pump blood.

To ensure you are adequately hydrated, make these your good water habits: Drink water before every meal and during and after exercise, and have a bottle nearby to sip throughout the day or whenever you feel thirsty.

Glasses of water
Credit: Victor Protasio

Water Before Food

Studies show that people who drink a glass of water before their meal eat fewer calories. "Water has zero calories, and drinking a glass of water before a meal can fill you up and help you eat fewer calories at a meal," says Lisa Drayer, registered dietitian and author of The Beauty Diet. And water doesn't have to come only from the tap. "Research reveals that water-rich foods like salads, vegetables, and soups can also help you lose weight," Drayer says.

Beyond Water

Coffee with milk
Credit: Victor Protasio

You can stay hydrated with beverages other than water. These all count toward daily fluid needs:

  • coffee/tea
  • smoothies
  • sports drinks [during 90 minutes of exercise]
  • sparkling water
  • sugar-free electrolyte drinks

Coffee Counts!

Despite its undeserved reputation for being dehydrating, your cup of coffee can actually contribute to your fluid needs. It all depends on how much coffee (or tea) you're consuming, Drayer says. "Consuming more than 300 milligrams of caffeine can cause fluid loss, though you can add a small amount of milk to offset this." (A regular cup of coffee has between 50 and 150 milligrams of caffeine.) And don't fret that you will pee out all the hydration benefits: According to Harvard Men's Health Watch, you still keep more fluid than you lose.

The Magic of Milk

Water isn't the only way to hydrate, according to a study from Scotland's University of St Andrews. A drink with just a little fat, sugar, or protein will actually keep you hydrated longer. Dairy milk, which has a little of each, is one of your best choices. Those nutrients help slow your body from emptying the fluids. Milk also has sodium, which helps us put the fluid to good use.

Sugar-Free Flavor

Infused Waters
Credit: Meredith

If water is too plain to entice you to drink enough, try adding citrus or cucumber slices or fresh berries for more flavor.

Juicy Fruit

Watermelon wedges
Credit: Victor Protasio

93% = The percentage of water in a watermelon (in case you were wondering how it got its name!). Here's how to make thirst-quenching watermelon drinks.

The Dry Skin/Water Myth

As much as we've heard that drinking lots of water will help dry skin, there's not great evidence that it's true. According to dermatologists at the University of Arkansas, dry skin — which may be rough, itchy, flaking, scaling, or peeling — is an external problem that should be treated from the outside. Dry skin lacks oils, which is why topical moisturizing creams can help.

Your skin is a giant organ, however, and like all your other organs, it needs to be properly hydrated. Dehydrated skin is different from dry skin. Dehydrated skin may be itchy and dull and cause dark under-eye circles, as well as darkness around your nose that looks like shadows. Here's the good news: While dry skin can be challenging to rectify, dehydrated skin just needs you to drink water.

Thirsty Eyes

Do you sit in front of a computer screen all day? The glasses you need may be the kind you fill with water! People who stare at screens all day blink significantly less often — and blinking is one of the ways we keep our eyes lubricated. "Dry eyes can contribute to blurry vision," notes optometric physician Dr. Steven Weisfeld. "People who sit at computers all day should drink more to stay better hydrated, which helps keep their eyes from drying."

Can I Drink Too Much? (Water, that is!)

Drinking too much water can cause low sodium concentration (hyponatremia) in the blood, but it's rare and typically only happens during endurance events such as a marathon. While most people don't need to worry about drinking too much water, it still makes good sense not to chug an oversized bottle of water all at once. Keep a water bottle with you and sip throughout the day. You don't want to down your daily needs all in one sitting — that puts too big of a burden on your kidneys.

This article originally appeared in the June/July 2020  issue of Allrecipes Magazine.