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The Hiker's Guide to Staying Hydrated and Treating Dehydration

A hydrated hiker is a happy hiker. Feel good and crush miles with these tips for identifying and avoiding dehydration.

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Your body is between 55% and 60% water—when you’re properly hydrated, that is. Keeping it that way is imperative for performance, comfort, and safety on the trail, and it’s not necessarily as easy as “just drinking.” Learn how to establish good drinking habits and avoid the pitfalls of dehydration with our experts’ advice on one of the outdoors’ most fundamental skills.

How much water should I drink?

The answer depends on your climate, altitude, level of exertion, and, of course, each hiker’s own needs. At moderate temperatures and activity levels, drinking to satisfy your thirst should be enough. If you’re hiking in extreme heat or at altitude, pay closer attention: Up your intake to one liter per hour if you’re hiking at elevation or in a hot, dry climate. Increasing your exertion will also require you to up your water intake to replace fluid loss from perspiration and respiration. Lastly, no two hikers need exactly the same amount of fluids to stay hydrated. Use personal experience to guide your true hydration needs. If you’re not sure that you’ll have reliable access to water, pack a little extra.

Tips for Staying Hydrated

  • Hydrate before you leave your doorstep, car or camp. Drinking 16 to 24 ounces of water in the hour before you hit the trail is ideal for making sure you start trekking hydrated. Drink a little extra if you’re starting out first thing in the morning, as you’ll be dehydrated from the previous night’s sleep. 
  • Drink small amounts frequently, instead of chugging a liter every 2 to 3 hours to help maintain hydration levels for the duration of your hike. Set a timer every 15 to 20 minutes to remind you to take a few sips if you find yourself frequently forgetting to drink. 
  • Keep your water accessible. Hydration vessels and packs are perfect for this, as they make it easy to sip water while walking. If you prefer hiking with a water bottle, make sure to pack it on the top or outside of your pack, so you don’t have to do extra digging to retrieve it from the bottom of your bag. Hydration belts and vests are good options for trail runs and short before or after work hikes. 
  • Replenish electrolytes if you’re hiking for over an hour to make up for those you sweat out. Commercially available sports drinks like Gatorade are usually too sugary. Water them down, use a purpose-made powder or tablet like Nuun or Skratch Labs, or make your own by adding table salt and a splash of fruit juice to your bottle. Alternatively, pack salty snacks to boost your electrolyte levels throughout your hike. 
  • Refill water when you can. Always purify trailside water sources using a filter or chemical disinfectant or by boiling before drinking to avoid getting sick.
  • Drink a liter every time you stop to refill your water supply. You’ll rehydrate and avoid carrying extra water on the trail. 
  • Drink no matter the weather. Proper hydration is just as important in cold weather (being dehydrated makes you cold faster) as it is on a hot summer day. Hate sipping icy water on winter hikes? Pack a thermos or insulated water bottle filled with hot tea or warm water to keep you toasty and hydrated. 
  • Protect yourself from the sun with sunscreen, sun-protectant layers and a hat. Sunburns speed dehydration, and shade (from your hat) will keep you cooler, less sweaty and therefore more hydrated.
  • Hike when it’s cooler. In extremely hot climates, begin hiking at sunrise and walk till around 11 a.m. Then find a shady spot to rest and refuel with a large meal (don’t forget to rehydrate) until 2 or 3 p.m., when the sun is not longer at peak strength, and hike again until sunset.
  • Check your pee. Your urine should be light yellow, and you should have to go every couple hours. Low volumes of dark-colored urine every 4+ hours is a sure sign you’re dehydrated. 
  • Rehydrate with at least 16 ounces of fluids on the way home or at camp on overnights. This is also an excellent time to replace electrolytes by enjoying a post-workout sports supplement or tall glass of chocolate milk to promote muscle recovery and replenish sodium and potassium levels.

How to Tell if You’re Dehydrated

Dehydration is serious business, and the longer you wait to treat it, the worse of a problem it becomes. Follow the tips above to prevent dehydration before it starts, but remain aware of the following signs and symptoms to check yourself and your hiking partners for mild dehydration before symptoms become severe.

Early Signs of Dehydration

  • Thirst. That’s your body telling you to drink more water. Drink up the moment you feel thirsty. It means you’ve already gone too long without water. 
  • Dry mouth. Again, heed your body’s warning and drink up immediately.
  • Decreased energy. Don’t assume you’re simply tired from hiking. Drink 8 to 12 ounces of water with a snack or added sports drink mix to boost your energy levels.

Severe Dehydration Symptoms

Stop, rest and rehydrate immediately if you begin to suffer from:

  • Muscle cramps
  • Dizziness
  • A headache
  • Severe fatigue and/or decrease in hiking performance
  • Nausea
  • The “umbles” (stumbling, mumbling, grumbling and fumbling)
  • Dark urine

At-Home Dehydration Test

Weight yourself before and after exercise. Your weight should be the same. If it’s not, rehydrate with 16 ounces of water or water mixed with a sports drink for every pound you’ve lost, and plan to carry that much more water on your next excursion of a similar length and difficulty. Still losing a pound or two of water weight on the trail? Don’t worry about it. It’s incredibly difficult to maintain perfect hydration during strenuous efforts. Compensate by immediately rehydrating after intense hikes or train runs.

dry arroyo
Following a dry arroyo may lead you to pools of water.National Park Service

How to Treat Dehydration

  1. Stop hiking and find the closest available shade (if it exists).
  2. Sit down and rest, especially if you feel dizzy or are beginning to lose coordination.
  3. Rehydrate with water mixed with a dash or two of salt or a sports drink.
  4. Cool your body temperature by soaking a bandana, hat or shirt in water and applying it to your head, the back of your neck and the insides of your wrists.
fossil creek
Fossil Creek in Coconino National ForestDeborah Lee Soltesz/USFS

What if I run out of water?

You’re miles from the nearest known water source and just drained the last sip from your hydration bladder. First, stay calm. Then:

  1. Stay calm. Yes, we just said this, but it’s the most important step. Panic, and you’ll just waste time and energy.
  2. Assess your situation. How far is the nearest water source? Unless it’s punishingly hot, a few hours without water is more likely to be uncomfortable than dangerous. If you’re further out than that, you may need to find the wet stuff first.
  3. Find a nearby vantage point and scan the nearby terrain for vegetation, which is a sure sign of moist soil. Look for livestock, which tend to graze near water.
  4. Can’t identify a watering hole? Try hiking up or down a dry streambed; you might find an isolated pool, or at least moist soil where you can dig for water.

How to Avoid Overhydration

While less common, overhydration, also known as hyponatremia, can be just as dangerous as dehydration. It occurs when your blood sodium levels drop so low that your cells are unable to properly function.

The symptoms of overhydration are similar to dehydration: nausea, headache and fatigue. However, one key difference is one’s urine volume and color. If you’re peeing out a large volume of clear or near-clear liquid every 30 minutes to an hour, you’re overhydrated. 

To avoid it, pay attention to what and how much you’re drinking.

  • Don’t chug as much water as possible. Stick to a maximum of one liter per hour of exercise. If you’ve gained weight after exercising, you drank too much. 
  • Add electrolytes to your drinking water.

How to Treat Overhydration

  1. Stop drinking water.
  2. Pop a salt tablet or eat a salty snack (pretzels or chips are both good) to help increase your sodium levels.
  3. Rest until your energy levels return to normal. 

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