It’s easy to overlook, but staying hydrated is one of the most important things you can do for your brain. While we often focus on diet, exercise, and sleep to support cognitive health, hydration plays an equally vital role. Hollie Hristov, FNP, a specialist in Preventive Neurology, explains, “About 75% of your brain is actually made up of water. So cognition and long-term brain health can absolutely be affected if you're not properly hydrated.”

How Dehydration Affects the Brain

Even mild dehydration can disrupt cognitive performance and mood. “You can feel more cognitively fatigued if you're not adequately hydrated,” says Hristov. “You can see that in attention and in focus.” It can also impair memory. “You may have the inability to encode memories, both long and short-term,” she adds.

Dehydration can also lead to elevated stress hormones. “You may also have higher cortisol levels, which can in turn cause heightened stress responses,” Hristov explains. This cycle of dehydration and stress can wear on the brain and body over time.

Signs You’re Not Drinking Enough Water

While thirst is an obvious indicator, there are other signs of dehydration that are easy to miss, including:

Dry mouth or dry skin

Skin that doesn’t return quickly when pinched

Fatigue

Weakness

Headaches

Dizziness or lightheadedness, especially when standing up

Brain fog

Poor concentration and memory

Mood swings

Trouble making decisions

How Much Water Should You Drink?

“For optimal brain health, the amount of water you want to drink a day is probably two to three liters, ideally,” Hristov recommends. At a minimum, she advises aiming for at least six to eight cups a day.

Some people find it easier to start their day with water. “When you wake up in the morning, you're probably gonna drink a full glass of water. Some people add lemon, some people do hot water. That's probably the best way to start your day,” she says.

Throughout the day, consistency matters more than drinking large amounts at once. “You wanna drink the majority of your water throughout the day,” says Hristov.

She adds a helpful tip for those who wake up frequently at night to use the bathroom: “If you're one of those people that has to do that, maybe don't drink so much water after a certain amount of time at night or after dinner, so you're not getting up and down all night.”

When You Might Need Electrolytes

There are times when water alone may not be enough. “If you are in an environment where you are doing a lot of activity, like if you're at the gym and you're working out a lot, or if you live in a really hot environment, that's when you might wanna think about adding electrolytes to your water,” says Hristov.

You might also need extra fluids and electrolytes if you’re losing fluids due to illness and experiencing fever, nausea, vomiting, or diarrhea. “In those cases, basically when you're losing more fluids than usual, you might wanna think about adding electrolytes,” Hristov advises.

Staying Hydrated as You Age

“As we age, we may not have the drive to drink as much fluids as we did when we were younger,” Hristov explains. “But as we age it's super critical to stay hydrated because you're more at risk for urinary tract infections.”

For older adults, she recommends setting reminders. “We've had patients set reminders throughout the day to drink water, even if it's just like a small sip here and there,” she says.

If plain water isn’t appealing, there are plenty of ways to stay hydrated:

Add flavor with lemon, lime, or orange slices

Eat hydrating foods like cucumbers, watermelon, and oranges

Drink herbal teas

Include soups and broths in meals

Try hydrating candies or lozenges designed to boost hydration

The Takeaway

“Just staying consistently hydrated is key,” says Hristov. “Finding what works best and just kind of going with that and switching, and just trying new things just to get that water intake in.”

Whether through water, hydrating foods, or creative alternatives, maintaining good hydration is one of the simplest and most effective ways to support brain health and overall well-being.

To learn more about the benefits of hydration, watch our conversation with Hollie Hristov, FNP, in the video above.

By Alicia J. Barber, PhD