How Long Should You Run Without Water?

Drinking water is one of those things that we have to do whether we want to or not. When planning your run, it’s definitely more convenient to not have to bring a ton of gear with you, (or perhaps there are no bathrooms on the way)–how long can you run without drinking water?

You can safely run for up to an hour without drinking water at temperatures below 72F (~22C) and if you are of average weight. After that, how much and how often you drink depends on your sweat rate. The more you sweat, the more you should drink in order to maintain hydration.

You may be wondering whether it’s different according to fitness levels, or in hotter weather, or just when to run with water and when not to. We’ll have a look at everything you need to know to stay on track and prevent any hydration health hazards on your run.

By the way, as an Amazon Associate, I earn when buying qualified products through links on my site.

Here’s an opinion from Mark Lewis:

Do you REALLY need to run with water? | Mistakes I made when new
Mark posits that you don’t need as much water as you think.

How Long Can I Go Running Without Water?

It’s safe to run for about an hour at room temperature at a moderate pace for an average-weight person, however this should not be enough to tell you exactly how far you can run without water. The key to finding how much you need to drink is to find out how much you sweat.

Read on to find out how to do this.

Whether you take running seriously and train towards goals or compete in the sport, or just do it to keep mentally and physically fit, no runner wants to do harm to their body, short or long term.

Dehydration is the primary risk that you run by not drinking enough water on your run and should be avoided. Mostly, this is just a temporary condition, though, and doesn’t lead to any serious long-term medical conditions.

Each person has their own unique rate that they sweat. There are special devices to measure sweat but that’s not something you can find at Walmart, usually–one easy way to measure is to use this formula. The formula for calculating your sweat rate is:

sweating rate = pre-exercise body weight – post-exercise body weight + fluid intake – urine volume/exercise time in hours


While this may interest some, it is really not necessary to calculate your sweat rate in order to know how long you can go without water, unless you want to get scientific about it.

To make it easier, the average person sweats between 0.8 to 1.4 liters of water per hour of exercise. Sweating is good – a necessary function to help us to regulate our body temperature. A by-product of this regulation, though, is the loss of water.

Naturally, we need to replace it at some point to prevent our bodies from becoming dehydrated. The tricky part is being able to listen to our bodies to gauge when it’s time to replenish it or how long we can push ourselves to go without it.

How Much Should I Drink?

There are a number of factors that influence when and how much to drink during your run.

If you’d like an easy test to figure out whether you should be drinking, try this:

Weigh yourself (without clothes, especially after since clothes absorb sweat) before and after a run (taking a liquid into account -> 2.2lbs =1 liter of water).

If the loss in weight in weight is around 1-2% of your body weight, you’re right on point. If you’ve lost 2-3% or more, then you need to hydrate more for your runs.

StatusBody Weight Percentage Change
You’re drinking enough water+1% or -1%
Somewhat Dehydrated-1 to -3%
Very Dehydrated-3% to -5%
Danger Zone of Dehydration-5% or less
Data from University of Connecticut Field Advisory

So, if you normally weigh 150 lbs, then losing 2.2 lbs of weight after a run would be about 1.5% of your weight. You should drink at least a half-liter of water to compensate for that.

An Even Easier Way To Tell How Much To Drink

Doing math is fun–but an even better guide is to follow your thirst. A common misconception is that if you’re thirsty you’re already dehydrated. Thirst is a built-in mechanism our bodies have to tell you that you need to drink. Don’t ignore thirst or postpone it–it’s a surefire way to get to dehydration. (source)

Another super important thing to watch out for is your urine color. If you are peeing a dark yellow, then this is an easy sign that you’re not replacing your fluids fast enough.

Is It Bad To Run Without Water?

So we know that losing too much water causes dehydration and that how quickly you dehydrate will depend on a number of factors, but what does this actually mean, and is it really bad?

First, let’s look at some factors that can cause dehydration.

Factors That Cause Dehydration

  • Heat: If it’s hot outside, (77F/25C and above)
  • Wind: The windier it is, the faster your sweat evaporates.
  • Weight: The more you weigh, the more you sweat
  • Drinking Rate: Perhaps most obviously, if you don’t drink enough water you’ll get dehydrated.
  • Sodium Deprivation: not getting enough salt
  • Water Drinking Discomfort: I’m personally able to chug water really quickly, but my wife isn’t–if you are someone who has a difficult time drinking a lot of water at once, you have to be extra vigilant.

It is important to be able to recognize the signs of dehydration so that you don’t ignore them. While earlier signs can include thirst, a dry mouth, or a decrease in energy, some of the more serious symptoms can include:

  • Extreme thirst
  • Muscle cramps
  • Fatigue
  • Headaches
  • Nausea
  • A decrease in heart rate

Strategies to Prevent Dehydration

  • Salt. Though not good in large quantities in your diet, salt helps to retain water. When you sweat, you lose sodium too. In order to retain water in your body and help to stay hydrated, be sure to rehydrate with a sports drink that contains sodium, or else consider a salt tablet with water. Many gels contain sugar but not enough sodium, so pay attention to maintain a good balance.
  • Magnesium and potassium are also lost in sweat and play a vital role in fluid balance within your body, as well as muscle function, amongst others. Lots of fruit (including bananas) are rich in potassium, and dark chocolate and seeds are a couple examples of good sources of magnesium. Make sure that you get enough!
  • Listen to your body. There are a number of signs that your body will give you to indicate that it is dehydrated. Don’t just ignore them, but pay attention when your body is telling you to drink more.

You can put off feeling a little thirsty if you know you’re five minutes from home. But these other signs should not be ignored because they could be life-threatening. Water is crucial for a number of functions in the body, and starving your body of liquid for too long can cause this functioning to deteriorate.

Those functions specifically related to running include regulating body temperature, lubricating joints, and maintaining blood pressure. So drink up if you don’t want issues with any of these!

An easy thing to do is to remember is to drink before you run. How quickly your body becomes dehydrated, and therefore how long you can last without water, will depend on how hydrated you already are. This will vary according to the time of day that you run–it’s not a good idea to chug right before you head out, but just drink a half glass or so before you hit the pavement.

If you think that chugging a few liters of water just before you run is a good idea, “just to be safe” or because you know you aren’t sufficiently hydrated, think again. All this will do is essentially flood your kidneys, which will flush out all the excess, causing the need for frequent bathroom stops during your run. Your body needs to be hydrated for days before a race, and if you’re training, then you need to maintain hydration.

Summary Of Dehydration

Running without water per se isn’t bad. It just depends on:

  • how long you run for
  • how hydrated you are already
  • the mineral composition in your body at the time (e.g., Sodium levels)
  • individual sweat rate

When Should You Run With Water?

So you’ve established that running without water in many conditions is not a good idea. But what does that mean for understanding when you should run with water?

Let me summarize situations where you should bring water. If just one of these applies, I’d recommend bringing water.

  • You’re doing sprints
  • It’s hot outside (greater than 77F/25C)
  • If you’re running for more than an hour
  • If you’re overweight or obese
  • You’re running a route you never have before
  • It’s really windy (more than 20MPH)
  • You’re out of shape and haven’t gone running in a while

Aside from running the risk of dehydration, there is no conclusive research about whether to drink during short and medium-length runs. While not drinking during a short/medium run makes you thirstier afterward, it doesn’t significantly affect your performance, but that’s not the case for long-distance running.

Is It Possible To Drink Too Much Water?

It’s also possible to drink too much during running, which can cause gastrointestinal distress, which in extreme cases can cause water intoxication or hyponatremia, which can be deadly. It is key not to force water down but to listen to your body’s needs.

What happens is if you drink too much water your blood sodium can drop, which is critical for taking oxygen to your body systems. If you are running for long periods of time (greater than 4 hours), then it’s life-threatening to not hydrate with enough sodium. (source)

Don’t forget amongst all your considerations for drinking water before and during a run, and it is just as important that you hydrate properly afterward. Drinking a lot right after you run is a good idea, but then maintaining that will smaller amounts over the following few hours is key too.

It is likely you’ll be hungry, and so you will be eating too, but if you have just run a long distance, you should consider hydrating with liquids that also contain electrolytes and carbohydrates to ensure that your hydration and nutrition are optimal, replacing more than just the volume of liquid you’ve lost.

How Do You Carry Water While Running?

The last thing a runner wants is to feel weighed down while running. I’m one of those people that will do anything to not be unencumbered. I hate exercising while carrying stuff.

It’s much easier to just go without–I totally get that. But sometimes, especially when distance running, it’s necessary to carry water.

How can you do this without feeling like you’re carrying bulky, extra weight? We’ve got all the solutions for you.

An example of hydration gear
  • Pouch – these nifty little carriers tuck into your waistband and carry a small bottle. Not ideal for large volumes, but great for a compact little hydration boost.
  • Waistband belt – there are a number of options available, some with space for multiple bottles, and others that include a pouch. This is great if you want something secure around your waist with easy access, but without having anything knocking against you or movement of the bottles. Your hands are free, and the weight is carried around your middle, which some could even argue is better for training!
  • Hand-held carrier – multiple options exist of either bottles with easy grips held directly in hand or of bottles that fit into pouches (some with a zipper compartment for extras) with a handhold. If you don’t mind carrying something in your hand, this is a great option, with a variety of sizes available. Some even come in pairs so that the weight is distributed across both hands.
  • Water bladders with a backpack– this is a great option if you don’t mind wearing something on your back. Essentially a backpack of water, there is a tube leading from this water pack to your shoulder, secured for easy access to your mouth. Like the belts, this is a good choice for those who want to keep their hands free and centralize the weight of the water they’re carrying. Some backpacks are designed to fit within between your upper shoulder blades so you don’t have a huge sweat bath on your back.

If you want to see hydration tools for running, check out REI, here, or for more variety, you can see a ton of options on Amazon.

It’s not just about how you carry your liquid, but which liquid to carry! If you want to take hydration for a shorter run, water is recommended for anything under an hour. If you run for longer than an hour, consider sports drinks or another liquid with a mix of sodium, sugar, and electrolytes in it to replenish some of the minerals that you are losing and give you an energy boost.

Tips for Maintaining Hydration

There are a couple of measures you can take in order to prevent the occurrence of dehydration.

  1. Plan your route: Whether it’s a shorter run and you just don’t want to carry fluid, or whether it’s longer and you need to refill, try to plan your route to include going past water sources where you can take a quick sip or fill up. If you aren’t going past any such place, you could also use your car as a top-up point for hydration and snacks and loop past it before continuing.
  2. Set a timer: On longer runs, when you need to rehydrate frequently, you can often lose track of time. Set a time on a phone or watch to help remind you to drink regularly (for most people, this means every 15-20 minutes, so says REI). You don’t have to drink–but if you get in the zone, this is not a bad way to remember to check in with your body.
  3. Carry liquids with you: Stopping on the run is not ideal – it slows you down, messes with your rhythm, and if this is the only time you drink, you’ll likely not drink enough on a long run. Carrying something with you is the best way to keep the momentum going and make sure that you drink regularly.

By the way, have you wondered if your performance gets all messed up if you stop during a run? Check out our article, on the subject.

Should I Eat Before Running?

Drinking goes hand in hand with eating, and for those who prefer to run early in the mornings, it is not unusual not to eat beforehand, making staying hydrated an even more important factor to pay attention to! Just as you should be hydrated before you run, it is important to try to eat something before you run, too, to give your body the fuel it needs to function safely and efficiently.

What and how much you eat are just as nuanced as drinking before a run, but bananas, avocados, and slow-releasing carbohydrates are all good ideas. The distance that you run will also play a large role in what you should be eating pre-run. Just as drinking a lot immediately before a run can sometimes result in a cramp or a stitch, it is advisable to eat a small meal or snack before you run, and perhaps even several hours before if it is a large meal.

Overall, your body should have enough fuel, both liquids, and food, to sustain your energy levels for the duration of the run.


So we’ve figured out that though there are some general guidelines you can follow in figuring out how long you should run without water, there are also a lot of individual variables and no one absolute answer that will work for everyone. The key is to listen to your body and work out what works best for you! If you haven’t been in tune with your body, now’s the time to get in sync and learn to read the signs. Bottom line: Drink when you’re thirsty!


Peter is a software developer who loves to take every opportunity to go outside that he can get. Peter grew up going on long backpacking excursions with his family every Summer and now enjoys staying at the beautiful Texas State Parks and swimming in the amazing Texas Rivers.

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