Your body is made of about 60 percent water. That good old H₂O allows your body to perform all of its necessary functions, keeps your organs healthy, your skin clear and prevents waste from building up inside you.

Water doesn’t just circulate within you though—you lose water every time you breathe, sweat or use the bathroom. This is why you need to replenish it. Not getting enough water can lead to dehydration, which can be fatal in some severe cases, or cause confusion and sickness in others.

By now, you’ve probably heard the old rule that you should drink at least 8 cups of water a day. Nutritional experts have used this as an everyday recommendation, but it’s not a hard-and-fast rule. So, how much water do you really need per day, and why?

How much should you sip each day?

As mentioned, the recommendation to drink eight 8-ounce glasses of water per day isn’t based on exact science. It’s a very good baseline for the average adult, but, in reality, the amount of water you need to drink per day can change. It’s also determined by many factors, including climate, activity and biological sex.

In general, the real key is to sip on water continuously throughout the day and drink when you feel thirsty. The Institute of Medicine (IOM) recommends men intake approximately 13 cups of water, while women should have approximately 9 cups.

However, the only way to hydrate isn’t just by drinking pure, clean water. Water is contained in a lot of foods, especially fruits and vegetables, as well as in other liquids like milk, tea, coffee and even soda. When eating a diet filled with water-rich foods and drinking other liquids, the number of glasses of water you’ll need to drink may decrease.

You’ll need more water if you are pregnant or breastfeeding—approximately 10 cups, according to the IOM. Additionally, if you are exercising or outside on a hot day—doing activities that make you sweat a lot more than normal—you’ll need to drink a lot more water to compensate. Make sure to keep a water bottle handy during these activities so you don’t get dehydrated.

If sticking to the eight cups a day rule helps you remember to stay hydrated, that’s a good way to go. Otherwise, just listen to your body and make sure to drink when you feel thirsty! A glass of water with each meal is also a good idea, as well as one between meals.

That being said, don’t guzzle water all day (even when you don’t feel thirsty) to meet a minimum intake. There is such a thing as drinking too much water! By drinking an excessive amount of water, you can dilute the electrolytes in your blood, lowering your sodium levels. It’s called hyponatremia, and, although it isn’t all that common in average adults, it can be fatal.

The benefits of staying hydrated

Staying hydrated not only keeps the most basic functions of your body regular, it can help boost cognitive abilities, clear up acne and help you lose weight! Here are some of the benefits of staying well-hydrated every day:

• Improve mood: If you’re ever feeling a bit cranky, pour yourself a cold glass of water and finish it off, then re-assess. Chances are, you were starting to get dehydrated. Losing too much water has been proven to impair mood while increasing the frequency of things like headaches, which never brighten a bad day.
• Increase brain function: Not getting enough water can leave you feeling sluggish and unfocused. Studies have shown that fluid loss can impair cognitive function, leaving you confused or unable to concentrate on tasks.
• Boost metabolism: Many health experts have linked hydration with weight loss, and for good reason. In numerous studies, drinking water helped increase energy expenditure in the body. Hydrating before meals has also helped people reduce their appetites, resulting in fewer calories being eaten. Both of these things contribute to weight loss.
• Clear up skin: Your skin needs to stay hydrated, too, and drinking water can help bring color back to pale, dry skin. It can also help flush out toxins and clear up acne for brighter, firmer, clearer skin.
• Contribute to overall wellness: People who drink more water tend to stay healthier because their bodies can do what they were meant to do without getting dehydrated and slow. Hydrating allows your body to flush out waste and circulate healthy nutrients, keeping you happier and healthier day in and day out.

Studies have shown that health in every part of the body is directly linked to water. Make sure you keep track of how much water you’re drinking per day and carry around a water bottle, so you always have access if you start to feel thirsty. Having a bottle in front of you can help remind you to drink, even on busy days, so you can stay energetic and healthy!