Hydration for Runners: Everything you need to know!

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In this article, we give you all the information you need about hydration for runners, how to calculate your fluid needs, and ways to carry water with you on your next run.

Proper hydration plays a crucial role in our daily lives and in our sports performance. Improper hydration can lead to both dehydration or hyponatremia resulting in things like dizziness, fatigue, and poor running performance.

On shorter runs – say anything less than 5 miles or 8 kilometers – hydration shouldn’t be a huge issue.   If you’re out for 30-45 minutes, then unless you are running in the heat then it’s fine to replenish your fluids after you finish.

Once you get into longer distances, you’ve got to be mindful of your hydration levels.   If I go out for anything over a 45-minute run, I’ll be drinking water while I’m running.  

Many runners actually drink too much water, as opposed to not enough.   Drinking too much can lead to stomach slosh, or – much worse – hyponatremia if you completely mess up your salt balance.  

Likewise, dehydration during a run can lead to a headache after running and medical issues, and certainly doesn’t do your kidneys any good.  

In this post, we provide you with everything you need to craft your own hydration plan for your running workouts and races, as well as gear recommendations for carrying your water with you on your next run.

Hydration for Runners: Everything you need to know! 1

How much fluid do I need?

How much fluid you need actually covers 2 parts:

  1. How much fluid you need on a daily basis if you’re active.
  2. And how much fluid you need to consumer during your workouts and races.

Daily hydration is key for proper hydration during your workouts and races because you don’t want to start your workouts in a hydration deficit. It’s always a good idea to start your workouts fully hydrated.

General Baseline Hydration

In general, the recommended 8-10 cups of water a day is a good baseline, then you can adjust from there. If you are very active and do a lot of high-intensity exercise, or if you live in a hot or humid climate and you sweat a lot, you’ll need to increase your daily hydration.

Daily hydration also includes other liquids you drink, such as milk, juice, coffee, tea, etc. so you’re not just limited to plain water to meet your hydration needs.

Prehydrating Between Intense Workouts and Races

If it’s been less than 12 hours between intense workouts or races, you’ll want to pre-hydrate about 4 hours before your workout or race event.

For pre-hydration, slowly consume 5-7 ml (0.17-0.23 oz) of fluid per 1 kg (2.2 lb) body weight.

This is roughly the equivalent of a large glass of water for a 75kg average person.

If you are concerned about hydration during your workout or event, you can add some sodium-containing snacks or fluids with your pre-hydration routine to help with water retention.

Pre-hydration isn’t always necessary if there have been over 12 hours between workouts or you are already well hydrated. But it never hurts to keep tabs on your hydration levels before your running workout or race!

hydration for runners

How Much Should You Drink During Exercise?

The goal of hydrating during workouts or races is to prevent dehydration which would negatively impact your abilities or state. Having said that, some small level of dehydration is normal during prolonged workouts; you can re-hydrate well after your run.

With this in mind, the current research for performing activities where you sweat a lot is to just drink when you begin to feel thirsty.   

This has also been described as ‘drinking a sufficient amount to prevent thirst’ in the study that concerned it.

Running and Hydration – Here’s The Rule of Thumb

If you’re looking for an actual quantity of water so you can plan your hydration needs in advance, here’s the average consumption

In general, it’s recommended that athletes aim to drink 0.4-0.8 liters per hour (L/h) or 8-16 ounces per hour (oz/h).

How To Calculate Your Sweat Rate

But since your sweat rate is highly individual, you may wish to check your own sweat rate and fluid loss during running workouts or races to customize to your own needs.

Hydration for runners: everything you need to know

One way to check how much fluid you’re losing during workouts is to weigh yourself before your workout, complete your workout (without urinating at all during the length of your workout), then weighing again at the end of your workout to see if you have lost or maintained your weight.

If you have maintained your weight during the workout and your urine color is not dark or concentrated, then you are drinking enough fluids.

If you have lost weight during your workout and your urine color is darker, you need to increase your fluid intake during your running workout or race.

Here is a handy formula:

  • Sweat rate (ml/hr) = weight before exercise (g) – weight after exercise (g) + amount of fluid consumed (ml) – amount of fluid urinated (if applicable)/minutes of activity x 60
  • This formula will give you your a ml/h number that will show you how many ml of liquid per hour of activity you’ll need to plan for during your training runs and races and recovery.
  • If you are calculating this for a race, try to replicate conditions so you can estimate your fluid needs for the temperature and humidity you’ll likely experience.

It’s important to remember that some dehydration is normal during prolonged exercise, and attempting to replace your exact fluid quantity during exercise can be counter-productive and lead to stomach slosh: follow the sip rule outlined above and rehydrate the rest when you cross the finish line.

Another way is to calculate that 1 milliliter of sweat loss roughly represents a gram loss in body weight. So if you lost 0.25 pounds (113 grams) of weight during your workout, then you’d need to increase your fluid intake by 113 ml (about 4 fluid ounces) next time you workout under similar conditions.

The goal is to weigh the same after your workouts since any rapid weight loss is attributed to water and to prevent dehydration, you want a 1:1 replacement of fluid lost (including fluids you’ve consumed after your workout).

Once you’re done with your running workout, your goal is to replace any lost fluids from your workout (as well as electrolytes if needed), and then move into your regular daily hydration maintenance.

Hydration for Runners: Everything you need to know! 2

What are electrolytes?

When your sweat rate begins to increase, you’ll want to start adding in essential minerals (called electrolytes) to your hydration routine to replace lost minerals in your sweat.

You know how sweat is salty? It’s because you’re excreting these minerals.

Electrolytes are minerals that are considered essential for proper functioning of the human body and these minerals are often lost through sweat.

Electrolyte minerals exist as charged ions and include sodium, calcium, magnesium, and potassium (some lists include chloride and phosphorus as well).

These minerals are essential for cellular function and help to regulate pH in the body, and they are essential for nerve and muscle function (including the heart muscle).

With increased sweat rate, there is an increase in loss of these minerals. There are several factors that influence sweat rate:

  • Workout intensity
  • Humidity (people sweat more in high humidity)
  • Heat
  • Genetics
  • Gender (men in general tend to sweat more than women, although this is not always the case)
hydration for runners

The amount of sweat people lose during workouts can be highly individual, as well as the mineral makeup of their sweat. Some people lose more salt in their sweat than others do, so it’s important to learn more about your body’s individual sweat rate (we’ll show you how to calculate that next!).

If you know that you’re going to be doing a race or event in a hot and/or humid climate that you’re not used to, take some time to acclimate yourself to the climate beforehand to not only perform better, but also to help your body adjust to new hydration needs.

bottle of gatorade next to a pond

Hydration options for runners

There are many different hydration options available to runners and fitness enthusiasts, and sometimes the number of options can be overwhelming!

But we’re going to break down the main types of hydration products available and what products are best for you and your fitness needs.

Plain water

Plain water is the best thing to start with for regular daily hydration. For most people and recreational exercisers, plain water will suffice for hydration if your workouts are 1) moderate in intensity, last less than 1 hour long, and 3) are in cool temperatures in low humidity.

But once you start to increase your workout length, workout intensity, ambient temperature, or humidity, your hydration needs change based on an increased sweat rate and greater loss of electrolytes and minerals through your sweat.

When any (or all) of these factors change and your sweat rate increases, you’ll need to start adding electrolytes to your hydration regimen to replace lost minerals since plain water alone won’t be enough.

While plain water is inexpensive/free and is great for most workouts, it isn’t enough if you sweat a ton and your workouts are long.

Electrolyte hydration options

Once you start to sweat more due to higher temperatures, more intense workouts, longer workouts, etc. you’ll need to switch from plain water to an electrolyte to replace minerals lost during heavy sweating.

Electrolytes come in several different forms for you to choose from:

  • Pre-mixed drinks
  • Powders or tablets you mix with plain water
  • Capsules you swallow as a supplement
  • Chewable tablets (like Salt Stick fast chews)
  • Electrolytes mixed into energy chews and gels

The type of electrolyte you choose will depend on your workout, your palate, your fueling needs, and how you plan to carry your hydration during your workouts.

Also, every brand of electrolyte replacement has a different formulation. So some brands will have more sodium, others will have more potassium, and still others (like Ultima) will have trace minerals included like selenium and copper (I’ve found my body really likes these ones!).

Try out and research a variety of different brands to see which ones work the best for your body.

Most electrolyte powders are sugar free, so if your workouts aren’t long or you plan on having a separate fueling plan with carbohydrate chews, gels, or actual food, then the sugar free electrolyte drink mixes will work well for you.

If your workouts are going to be long and you are able to refill a water bottle, it’s great to keep electrolyte drink mix packets or tablets (like Nuun) with you to add to water at your convenience.

If your workout isn’t going to be long, but you need electrolytes because it’s hot or you’re a heavy sweater, then you can take a small bottle of pre-mixed electrolytes with you or a few electrolyte chewables if you’re not taking very much liquid with you on your run.

It’s important to note that while you may like the idea of a chewable tablet or capsule, if you’re doing a race, you might not be able to stomach a chewable or be able to easily swallow a capsule.

Make sure to always train with your planned hydration methods before racing! Don’t try new electrolyte or hydration methods during a race that you haven’t tried beforehand during training sessions.

Remember: this all takes practice to figure out an electrolyte replenishment strategy that will work for you! Have some fun trying out some new methods and brands during your training runs to see what works best.

Related: How Frequently Should You Take Energy Gels During Races?

Sports drinks that contain carbohydrates and sugar

Sports drinks that contain calories and sugars typically aren’t necessary for regular intensity workouts that are under 1-1/2 hours, so it’s okay to skip these during and after your regular workouts.

But they are helpful for adding easily digested calories if you are doing endurance running where you need a carbohydrate fueling strategy.

A sports drink that has different kinds of sugars (like glucose and fructose) along with electrolytes is very helpful in this case and is a great thing to have on hand for quick fueling.

Just like with electrolyte powders, not every carbohydrate sports drink is made the same, so look into different brands to see what works for you. Certain types of sugars do not agree with some people (like people with IBS have a difficult time digesting fructose), so look for sports drinks with sugars that you can tolerate during heavy exercise.

Sports drinks are an easy way to consume calories for your fueling strategy during endurance running since some runners cannot stomach solid food (or even gels or chews) during an endurance race.

Make sure to plan ahead and count your sports drinks, gels, chews, and/or food into your entire fueling plan. If you overdo it with the carbohydrate fueling all at once, you may end up with an upset stomach as your body tries to handle multiple concentrated carb sources while you’re exercising.

Risks of poor hydration

Making sure that you pay attention to your hydration is not only important for optimal athletic performance, but it’s crucial to your health and wellbeing!


Most people aren’t going to get dehydrated to the point of serious health consequences or death, but many people do experience dehydration symptoms like lethargy, muscle cramping, dizziness, confusion, etc.

Mild dehydration (1%-2% loss of body weight during exercise) is normal during exercise, especially during endurance events like marathons. But your goal should be to manage mild dehydration and keep it from becoming severe dehydration that can result in serious complications like seizures.

Other symptoms of dehydration include:

  • lightheadedness
  • thirst
  • fatigue and lack of energy / enthusiasm
  • lack of need to use the bathroom
  • dry mouth
  • constipation


One aspect of hydration that people don’t often address is hyponatremia, which is over hydrating (the opposite of dehydration).

Hyponatremia is defined as an abnormally low concentration of blood sodium and it can occur when someone drinks too much low-sodium fluids over long periods of time compared to their sweat rate.

The greatest predictor of hyponatremia is an increase in weight during the duration of a workout, meaning you have consumed an excess of fluids.

Runners who are exercising at low to moderate intensity for long periods of time and who have a low body mass index are more susceptible to hyponatremia, while high intensity exercisers are more likely to suffer from dehydration.

To prevent this, make sure that you are consuming moderate amounts of liquids for your needs during exercise, and you are also including sodium and electrolytes in your hydration routine when you’re running for longer periods (over 1-2 hours)

How to hydrate during your run (and how to calculate how much water you need) - Marathon Handbook

How to stay hydrated while running

Once you’ve figured out how you want to stay hydrated for your training runs and races, the next task is figuring out how you can stay hydrated during your runs.

Here are some ways you can plan hydration for your running workouts or races:

  • Plan out your route to go by places with water (like drinking fountains). If you need to do a longer run but can’t carry water with you, create loop routes where you can come back to a water bottle regularly.
  • Check out our recommended running vests – many of which come with hydration functions.
Best Hydration Tips for Runners - Marathon handbook
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Sarah Jane Parker is a food and healthy living blogger at The Fit Cookie, an ACSM Certified Personal Trainer, ACE Certified Health Coach, Revolution Running certified running coach, YogaFit Level 1 certified yoga instructor, and an ACE Certified Fitness Nutrition Specialist.

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