Drinking water just when you feel thirsty is enough to stay hydrated.

If you’ve spent any time on social media or visited a sporting event lately, you’ve surely been bombarded with incentives to drink more water. Influencers and celebrities drag water bottles around like it’s the newest fashion accessory.

On Twitter, robots constantly remind us to take more time to hydrate. Some reusable water bottles even come emblazoned with phrases to encourage drinking throughout the day – “Remember your goal”, “Keep drinking”, “Almost finished”.

The purported benefits of ample water consumption are seemingly endless, from improved memory and mental health to increased energy and prettier skin. “Stay hydrated” has become a new version of the old “stay well” greeting.

But what exactly does “staying hydrated” mean? “When laypeople discuss dehydration, they mean the loss of any fluid,” said Dr. Joel Topf, nephrologist and assistant clinical professor of medicine at Oakland University in Michigan (United States).

But that interpretation “is being completely exaggerated,” said Kelly Anne Hyndman, a kidney function researcher at the University of Alabama at Birmingham. Staying hydrated is definitely important, she said, but the idea that the simple act of drinking more water will make people healthier is not true. It’s also not correct that most people are chronically dehydrated or that we should be drinking water all day.

From a medical point of view, Dr Topf added, the most important measure of hydration is the balance between electrolytes like sodium and water in the body. And you don’t need to drink glasses and glasses of water throughout the day to keep it off.

How much water should I really drink?

We’ve all been taught that eight glasses of water a day is the magic number for everyone, but that idea is a myth, said Tamara Hew-Butler, an exercise and sports scientist at Wayne State University.

Single factors such as body size, outside temperature and how much you breathe and sweat will determine how much fluid you need to drink, she said. A 90 kg person who has just walked 10 miles in the heat will obviously need to drink more water than a 55 kg office manager who has spent the day in a temperature-controlled building.

The amount of water you need in a day will also depend on your health. Someone with a medical condition like heart failure or kidney stones may require a different amount than someone taking diuretic medications, for example. Or you may need to change your intake if you are sick, have vomiting or diarrhea.

For most young, healthy people, the best way to stay hydrated is to simply drink when you feel thirsty, Topf said. (Older people in their 70s and 80s may need to pay more attention to getting enough fluids, because the feeling of thirst may decrease with age.)

Despite popular belief, don’t rely on urine color to accurately indicate your hydration status, said Dr. Hew-Butler. Yes, it’s possible that dark yellow or amber urine could mean you’re dehydrated, but there’s no solid science to suggest that the color alone calls for a drink.

Do I have to drink water to stay hydrated?

Not necessarily. From a purely nutritional standpoint, water is a better choice than less healthy options like sugary sodas or fruit juices. But when it comes to hydration, any beverage can add water to your system, said Dr. Hew-Butler.

A popular notion is that drinking caffeinated drinks or alcohol will dehydrate you, but if that’s true the effect is negligible, Topf said. A 2016 randomized controlled trial of 72 men, for example, concluded that the hydrating effects of water, beer, coffee and tea were nearly identical.

You can also get water from what you eat. Liquid-rich foods and meals, such as fruits, vegetables, soups, and sauces, contribute to your water intake. In addition, the chemical process of metabolizing food produces water as a by-product, which also increases your intake, Dr. Topf said.

Do I need to worry about electrolytes?

Some sports drink ads might make you think you need to be constantly replenishing electrolytes to keep your levels in check, but there’s no scientific reason why most healthy people should drink drinks with added electrolytes, Hew-Butler said.

Electrolytes such as sodium, potassium, chloride and magnesium are electrically charged minerals that are present in body fluids (such as blood and urine) and are important for balancing the water in your body. They are also essential for the proper functioning of the nerves, muscles, brain and heart.

When you become dehydrated, the concentration of electrolytes in the blood increases and the body signals the release of the hormone vasopressin, which reduces the amount of water released into the urine so you can reabsorb it back into the body and regain balance, said Dr. . Hyndman.

Unless you’re in an unusual circumstance—exercising very intensely in the heat or losing a lot of fluid through vomiting or diarrhea—you don’t need to replenish your electrolytes with sports drinks or other products laden with them. Most people get enough electrolytes from food, said Dr. Hew-Butler.

Drinking more water, even without thirst, will improve my health, right?

Not. Of course, people with certain conditions, such as kidney stones or the rarer autosomal dominant polycystic kidney disease, can benefit from making an effort to drink a little more water than thirst would tell them, Topf said.

But in reality, most healthy people who blame their malaise on being dehydrated may be feeling sick because they’re drinking too much water, speculated Dr. Hyndman. “Maybe they get a headache or feel bad, and they’re like, ‘Oh, I’m dehydrated, I need to drink more,’ and they keep drinking more and more water, and they end up feeling worse and worse.”

If you drink at a rate beyond what your kidneys can excrete, the electrolytes in your blood can become too dilute and, in the mildest case, can make you feel “turned off”. In the most extreme case, drinking an excessive amount of water in a short period of time can lead to a condition called hyponatremia or “water intoxication”.

“It’s very scary and bad,” Hyndman said. If blood sodium levels get too low, it can cause brain swelling and neurological problems such as seizures, coma, or even death.

In 2007, a 28-year-old woman died of hyponatremia after allegedly drinking nearly 8 liters of water in three hours while participating in a radio station contest that challenged participants to drink water and then go as long as possible without urinating. In 2014, a 17-year-old football player in Georgia died of this condition after allegedly drinking 8 liters of water and 8 liters of Gatorade.

The condition has become so common among exercisers that when someone passes out during a run, rescuers are trained to consider hyponatremia, Topf said. Although the development of severe hyponatremia is rare in most healthy people.

How do I know if I’m well hydrated?

Your body will tell you. The idea that staying hydrated requires complex calculations and instantaneous adjustments to avoid dire health consequences is simply silly, experts said. And one of the best things you can do is stop overthinking.

Instead, the best advice for staying hydrated, according to Dr. Topf is also the simplest: drink when you feel thirsty. It’s really easy.

Translated by Luiz Roberto M. Gonçalves