How Much Water Should Runners Drink?

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Of course runners need to drink water – both before, during, and after a run. But how much water should runners drink while they’re running? How do you know if you’re drinking too little… And is there such a thing as too much?

Getting your hydration right could be the factor that supercharges your performance. So we’ve compiled a quick guide on determining the optimal amount of water to see you through your runs. Let’s dive in!

Why Hydration Matters

Whether you’re exercising or not, staying well-hydrated is essential for good health. Did you know that 60 to 70 percent of your body is water? The brain comprises between 75 and 95 percent water, and the lungs about 90 percent.

That’s not just coincidence—every major process in the body requires water to work, whether transporting nutrients or removing waste.

Staying hydrated can help you lose weight, improve your skin, keep your brain sharp, and aid in digestion. So it’s easy to see that water is essential for everyday life and health.

But it also plays an important role in your running. Dehydration brings many negative effects that can impact your training.

How Dehydration Can Affect Your Running Performance

Dehydration can quickly begin to lower your running performance. Some signs and symptoms include fatigue, muscle cramps, and loss of coordination.

As well as some nasty physical effects, dehydration can also lead to impaired cognition. A 2% drop in water weight is shown to hurt things like attention span, problem-solving, short-term memory, and coordination.

How Much Water Should Runners Drink?

The right amount of water differs from runner to runner. A 6 foot 4, muscular runner will have different hydration needs to a 5 foot 1 petite woman. The key to figuring it out is to determine your sweat rate, which will give you a good basis on how much to drink.

Determine Your Sweat Rate

To determine your sweat rate, you’ll need to set aside an hour to go for a run. If an hour is too long to run comfortably, stick to 30 minutes and adjust your calculations.

Step one is to weigh yourself before your run, sans clothes if possible, so you don’t have to deal with extra weight from clothing. Take note of this number. Now it’s time to run!

On your run, keep track of how much you drink. When you’re done, weigh yourself again—minus the sweaty clothing. Now for the mathematics.

Subtract your after-run weight from your pre-run weight. This gives you the amount of weight you lost during your run. Let’s say you lost a pound of body weight. Convert that to ounces—in this case, 16 ounces—and that’s the amount of water you lost in sweat.

Add the total amounts of water you drank to that number. Let’s assume you drank 12 ounces of water in total. That means you need 28 ounces—16 + 12—in one hour of running to stay hydrated. That equals 7 ounces every 15 minutes.

It’s a good idea to do one of these runs every few months as the seasons change. Your sweat loss in winter will probably differ from your sweat rate in summer.

Consider the Duration of Your Run

Remember, your individual sweat rate calculation determines how much you lose in one hour. If you’re running for longer or shorter than that, you need to adjust accordingly. Once you know your hourly sweat rate, consider the duration of the run you’re doing to nail down your numbers.

If you plan to run for 30 minutes, divide your final total by 2. If you want to run for 2 hours, double it. And so on. You may need a calculator for some!

Factors That Affect Your Hydration Needs

It’s great to know your individual sweat rate because you can start to cater to your own hydration needs. But it’s also important to know that certain factors can increase your water intake needs, so you’ll need to consider these on top of your sweat rate.

Running Intensity and Duration

We’ve already spoken about duration. But your running intensity also plays a role. If you’re doing an easy run, you’ll most likely sweat less than doing an intense session. You’ll probably need more water during intense runs—you may have to drink every 10 minutes, so taking more water than your sweat rate suggests is a good idea.

Weather Conditions

You’ll likely sweat more than usual on hot, humid, or windy days. If you’re heading out on a run when the weather is hot, it’s a good idea to take more water than your calculation suggests to account for extra fluid loss through sweat.

This will ensure that you maintain the optimal hydration level while you run.

Body Weight

Heavier people often sweat more as they have more body mass to move. This means the body generates more heat as they’re exercising.

If your body weight has changed significantly since you last did a sweat rate test, you may need to increase your usual water intake. It’s a good idea to do another test to ensure accuracy.

Altitude

The higher the altitude, the more you’ll at risk of losing water. If you already live and train at a high altitude, you shouldn’t worry too much about this. But this is essential information to know if you’re traveling for a race. Carry more water than you think you need when running at higher altitudes.

Running Terrain

The rougher the terrain, the more intense your run will likely be. This can up your water needs, so it’s a good idea to scope out the terrain of your run first if you’re doing a trail run. Rocky terrain means you should consider carrying more water than your sweat rate suggests.

Hydration Strategies

The easiest way to determine your hydration strategy is to go on the duration of your run. If it’s hot, humid, or windy, you might need to adjust these strategies to carry more water than suggested.

Running for 20 to 30 Minutes

Typically, you can avoid carrying water on a short run like this. Ensure you’re well-hydrated when you step out the door and hydrate when you return. But you don’t need to carry a bottle if you only go for a short one.

However, if it’s particularly hot or you’re running hard, you may want to drink more water since you’ll lose more fluids than on those easy runs.

If You’re Running for 30 to 60 Minutes

You’ll need to carry water with you for runs between 30 and 60 minutes. While it’s not typically enough time to become severely dehydrated, you’ll need to drink regularly to perform at your best. Try drinking about 4 to 7 ounces at around 15 minutes, 30 minutes, and 45 minutes.

You generally don’t need an electrolyte supplement for runs of this length. Fill your bottle with cool, pure water, and you’ll be good to go!

Long Distance Runs That Lasts Longer Than 60 Minutes

If you’re going to be out for longer than 60 minutes, then you should add an electrolyte supplement to your hydration strategy. At this point, your fluid/electrolyte will start becoming unbalanced as you replenish the water you’re losing, not the electrolytes.

An electrolyte imbalance can manifest in unpleasant ways, including severe muscle cramps and sudden-onset nausea. So it’s wise to get ahead of this and add an electrolyte tablet to your water about an hour into your run.

Consider using sports drinks that contain carbohydrates for an energy boost. These are often more helpful for 2+ hours, but they’re worth keeping in mind.

Both sports drinks and electrolytes come in powder or tablet form and can be added to your water.

We recommend avoiding sports drinks loaded with sugar and containing high levels of stimulants like caffeine.

Recognizing the Signs of Dehydration

It’s helpful to know the signs of dehydration so you know how to tell when your body is asking for more hydration. Here’s what you should be looking out for.

Mild early Symptoms

Thirst is the first symptom of mild dehydration. The moment you notice you’re thirsty, it’s a sign that you’re already dehydrated. It’s often also accompanied by a dry mouth feeling and increased fatigue.

As Dehydration Progresses

As your core body temperature increases and you continue to run without adequate hydration, the symptoms of dehydration will progress. You may start to develop a headache, your heart rate will increase, your muscles could start cramping, and you might feel nauseous.

Your running performance will be greatly reduced as you begin to feel fatigued, and you may experience dizziness.

Symptoms of Severe Dehydration

One of the telltale signs of severe dehydration is not sweating. When your body is short on fluid, there’s nothing to sweat out, so pay close attention to your body. If you’ve suddenly become hot and dry, you need to take action to rehydrate immediately.

You might also be urinating less frequently or not at all, although this can be difficult to notice when you’re in the middle of a run. But if you do get a chance to make a quick stop, check your urine color.

The yellow urine can tell you how dehydrated you are, especially as it may range in color from amber or even a dark brownish color. If you notice either of these symptoms, we highly advise cutting your run short and getting fluids in as quickly as possible.

Tips on Staying Hydrated While You Run

Here’s our best advice to help you stay well-hydrated while you run.

Drink Water at Regular Intervals

Take a few sips of water every 15 to 20 minutes during your run; there’s no need to drink every few minutes—but try different intervals to see what works best for you. For some, every 5 minutes might be optimal. For others, every 20 minutes could be good.

If you struggle to remember to sip, you can set an alarm on your smartwatch to remind you to drink. After a few weeks, it should become a habit!

Wear a Hydration Vest or Running Belt

A hydration vest or running belt will allow you to carry more water than just a water bottle. A belt can usually carry a bottle or two, and a vest should be able to carry a hydration bladder as well as a few bottles, upping your volume.

For long runs, you can’t beat a hydration vest. It allows you to carry quite a bit more water than any other carrying method, and it’s also fairly comfortable, giving you a hands-free drinking experience.

Freeze Water Bottles for Long Runs

If you’re going on a long run, you can freeze a bottle of water and take it with you. That way, your water will stay cool throughout the run, and you’ll be able to drink as it melts. Keep in mind that it may feel different to carry a frozen bottle!

But having a sip of cold water on a hot day can be refreshing and help keep you cool.

Plan Your Route Around Water Sources

This is especially important if you’re on a long run and can’t carry enough water with you. If you don’t want to invest in a hydration bladder, the best way to ensure you’ve always got enough water is to plan your route around available water sources.

Water fountains, coffee shops, or even your car could be a stopping point. Remember that if you’re training for time or speed, stopping to refill your water bottle will hamper that.

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AUTHOR

Ben is an avid road and trail runner, and has completed multiple marathons and ultras. A former running store owner, he now shares his knowledge and experience writing these articles.

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