According to Jennifer Williams, MPH, hydration scientist with Abbott, it’s easy to forget how altitude impacts your hydration levels, especially after a busy day of traveling. However, when acclimating to an area that sits well above sea level, you might notice some (rather unpleasant) altitude-related side effects—especially concerning your hydration levels. (Think places like The Mile High City, aka Denver, Colorado, which sits at an elevation of 5,280 feet, or Bogotá, Colombia, that’s 8,612 feet above sea level.)

The Centers for Disease Control and Prevention (CDC) says elevations at 8,000 feet above sea level or higher (but not limited to) can put you at increased risk for altitude sickness, which is caused by low oxygen levels in the air. To that end, it’s important to understand the potential impact altitude can have on hydration (or worse, dehydration) and how it can affect your daily activities, like exercising. To learn more about how high altitude and dehydration go hand in hand, we caught up with a hydration specialist, medical doctor, and sports dietitian to understand the appropriate measures necessary to stave away any elevation-related woes.

How altitude impacts hydration levels

According to Williams, folks that live at (or slightly above) sea level—for example, New York City, which is just 33 feet above sea level—are typically in the clear. However, when exposed to high-altitude areas—like the Rocky Mountains, where ski slopes sit at 11,000 feet or above—things may start to feel a little different, especially concerning your hydration levels. “As you climb higher in altitude, air pressure drops, meaning there’s less oxygen to breathe, less humidity, and less moisture,” Williams says.

This means that strenuous activities like hiking, mountain climbing, skiing, or traveling by plane, paired with high altitudes and/or extreme weather (hot or cold), can quickly become a recipe for dehydration.

Caroline Cederquist, MD, a board-certified physician and founder and chief medical officer of BistroMD, agrees that exposure to altitude can make staying hydrated even more difficult and can result in several physiological symptoms. “Higher altitudes are associated with thinner air and lower oxygen levels, which makes it harder to breathe. More rapid or labored breathing is a sign that your body is working hard—in turn, heavy breathing can cause even more water loss,” Dr. Cederquist says.

“Higher altitudes are associated with thinner air and lower oxygen levels, which makes it harder to breathe. More rapid or labored breathing is a sign that your body is working hard—in turn, heavy breathing can cause even more water loss,” Dr. Cederquist says.

As such, staying on top of your hydration when traveling to a high-altitude destination is of utmost importance, especially if you’re not accustomed to this type of environment. “Whenever your breathing increases, it’s important to replenish your body. However, if you live full-time in a high-altitude area, your body will likely adjust to the altitude over time,” Dr. Cederquist says.

How can you tell if you’re dehydrated at high elevations?

Much like dehydration symptoms at sea level, Dr. Cederquist notes that one of the first signs of dehydration folks may experience is rapid, labored, or heavy breathing. “Take it as a signal to replenish your stores,” she says. As altitude-induced dehydration progresses, Dr. Cederquist says one may experience headaches, nausea, dizziness, and darkly-colored urine. Other signs of impending dehydration include chapped lips and dry skin.

That said, Williams cautions that some dehydration symptoms can easily go under the radar. “If you are hitting the snow slopes, you might be less likely to notice your body’s typical ways to warn you about dehydration, like sweating under layers of clothing and a reduced thirst mechanism,” Williams says.

As such, she stresses the importance of replenishing the body with fluids and electrolytes, especially at higher altitudes, before dehydration has a chance to set in. It’s also worth noting that the hydration expert says it can easily take the body one to three days to acclimate to a new altitude. So, even if you’re feeling alright from day one, you might not be totally in the clear just yet.

How to prevent altitude-related dehydration

Dr. Cederquist and Williams both agree that prevention is key. For Dr. Cederquist, this means consuming hydrating foods like watermelon, apples, or cucumbers. Meanwhile, Williams says pre-hydrating before arriving at your high-altitude destination can make a world of difference. “Before boarding that flight across the country, or enjoying a scenic hike, drink one or two cups of water,” Williams says. If you start to feel a sensation of thirst, this may mean that your water levels are already running low, and it’s definitely time to drink up.

However, according to Williams, a quick, easy, and, more importantly, fast way to quickly boost hydration and reverse the onset of dehydration is by drinking scientifically-designed electrolyte drinks like Pedialyte. “Dehydration is not just the loss of water; it’s the loss of key minerals, also known as electrolytes. You get your electrolytes throughout the day from what you eat and drink, but when you are losing an excessive amount of fluid, replenishing key electrolytes, such as sodium, potassium, and chloride, can go a long way in avoiding negative signs of dehydration like fatigue, dizziness or headaches,” Williams says.

To that end, as much as you may want to indulge in a post-flight celebratory drink, Williams says it’s important to “celebrate smartly.” “It’s easy to grab a drink when you’re waiting at the airport or to toast with friends the night before a long hike, but alcohol can contribute to dehydration. Avoid consuming alcoholic drinks if you plan to be high up in the air—cheers to smart hydration instead,” she says.

Which type of activity puts you most at risk for dehydration at higher altitudes?

According to Dr. Cederquist, exercising in high altitudes will lead to the most amount of dehydration in the shortest time, especially if you’re not accustomed to the changes in the environment. Leslie Bonci, MPH, RD, CSSD, LDN, the lead sports registered dietitian for the Kansas City Chiefs, notes that the body can lose fluid twice as fast through respiration when breathing more rapidly due to exposure to higher altitudes. Additionally, Bonci says folks might experience an increased urge to urinate more frequently, which can also contribute to dehydration-inducing fluid loss.

While exercising at high altitudes, Bonci says what you drink is just as important as what you eat. “During exercise at altitude, fluids are helpful and need to be carried with someone at all times,” she says. Along with the fluids, Bonci suggests pairing them with carbohydrates from dried fruit, honey sticks, energy chews or gels, or applesauce pouches.

TL;DR? Hydration is the name of the game, especially when engaging in physical activity at higher altitudes.

An RD shares a list of the most hydrating foods: