Ask any fitness expert to list a couple of common workout roadblocks, and dehydration will likely always make the cut. It's a killer! You need water to exercise—you thrive on it—yet so many women spend their days dehydrated. So, what gives? It could be because, when it comes down to it, you may not even know exactly when you're dehydrated. To solve that problem, we asked Greg Justice, an exercise physiologist at AYC Fitness in Kansas City and author of Mind Your Own Fitness, to list the top signs you need to get way more H20 happy:

You Have a Headache
Unless you're chugging water 24/7, your body is constantly losing fluid. That means you're also losing essential salts like sodium and potassium because those are in the fluids you're losing. Now get this: That salt loss actually changes the chemical makeup of your blood. Your brain, in turn, is super sensitive to that change—and it's that sensitivity that triggers a headache. Make sense? The headaches get even worse, too, depending on how much water you lose. "The more water you lose, the more your blood volume drops, which causes less oxygen flow to the brain," says Justice. "That causes your blood vessels to dilate, which can make your headache feel even worse." Moral of the story: Not enough water equals headache central.

MORE: 5 Ways to Make Water Taste Better (So You'll Drink More of It)

Your Pee is Extra Yellow
Eek…kinda gross, right? But it's true. The reason this happens is that your urine is over-concentrated with waste. "When you're fully hydrated, the waste is easily flushed out in a more efficient manner," says Justice. But when there aren't enough fluids in your body, the waste isn't as easily flushed out, so it stays there.

You're Constipated
Again, kinda gross. But again, totally true. And the reason is somewhat similar. See, water helps move your waste through your colon and out of your body. "But if that water isn't there to begin with, it won't be able to move your food waste onward and outward as efficiently," says Justice. Hence the constipation.

MORE: 10 Ways to Drink More Water

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Annie Daly

Annie Daly is a New York City-based freelance writer, editor, and author who specializes in wellness, travel, and culture. She is the author of Destination Wellness (2021), and co-author of Island Wisdom (2022). A former editor at SELF, Cosmopolitan, BuzzFeed Travel, Yahoo Travel, and Good Housekeeping, she has also written for a variety of publications, including Condé Nast Traveler, Vogue, Travel + Leisure, Marie Claire, InStyle, and AFAR, among others. To follow her work, find her on IG @anniemdaly and subscribe to her Substack, Destination Wellness.