Fluid And Electrolytes: A Complete Runner’s Guide

Have you ever touched your face after a run, and it feels grainy? Or look down at your arms, and they are covered in white particles? Those are salt crystals!

While we run, our temperature rises, and our bodies need to work to keep themselves cool. They do this by sweating.

By sweating, our bodies keep us safe from overheating, but in turn, we lose vital salts and nutrients. We need to fuel them with what they need and replenish fluid and electrolytes so they can keep performing at their best!

In this article on fluid and electrolytes, we are going to discuss:

  • What are electrolytes?
  • The different types of electrolytes and their functions.
  • Why a proper fluid and electrolyte balance is crucial for runners. 
  • The consequences of a fluid and electrolyte imbalance. 
  • Tips to keep a proper fluid and electrolyte balance. 


Let’s jump in.

Fluid And Electrolytes A Runners Guide

What are electrolytes?

As runners, we need to keep our fluid and electrolytes in check for optimum running results and general health. This goes beyond just hydrating with water. Specific components need to be included in our hydration for our bodies to work efficiently.

But, what are electrolytes?

According to the National Library of Medicine, electrolytes are “minerals in your body that have an electric charge. They are in your blood, urine, tissues, and other body fluids.”

The electrolytes found in our body are sodium, potassium, magnesium, chloride, phosphate, and calcium. We will go into detail about the most important ones for runners (in no particular order).

#1: Sodium

Sodium helps regulate proper fluid and electrolytes mineral balance, so you don’t get dehydrated. It also assists with muscle contractions and nerve function.

#2: Potassium

Potassium is used in various vital functions in your body, such as regulating fluid and electrolytes balance, nerve signals, and muscle contractions. It also promotes glycogen storage and aids in the transportation of nutrients.

Fluid And Electrolytes A Runners Guide

For us runners, if we don’t have enough potassium, it will be impossible for our muscles to properly contract, leading us to cramp up.

#3: Magnesium

Magnesium is used for energy production, metabolism, muscle and nerve contractions, muscle recovery, and general bone health

It also helps avoid cramping.

Why are electrolytes essential for runners?

There is a common misconception that runners can stay sufficiently hydrated with water only. But this is far from the truth.

Hydration isn’t just about replenishing fluid, but also minerals. When we sweat, we are not only expelling water but heaps of crucial mineral electrolytes, too. That’s the grainy feeling on your skin that I mentioned before!

Specifically for runners’ needs, replenishing these electrolytes helps us avoid muscle cramping and fatigue, regulates our heartbeat, and keeps our body well-hydrated. As you can imagine, it also aids in optimum performance.

If our body is functioning efficiently on a general-health daily basis, it will perform at its best while exercising as well. This is the goal!

Fluid And Electrolytes A Runners Guide

Consequences of Fluid and Electrolyte Depletion

If you don’t consume enough electrolytes along with your fluid intake, you could not only experience the familiar runner repercussions such as cramping and stitches but any number of issues that can affect your health. These include:

  • Confusion and poor decision making
  • Dizziness
  • Nausea
  • Irregular heartbeat
  • Fluid retention
  • Dry mouth 
  • Gastrointestinal problems

These are some of the most common effects of dehydration, but we should also mention overhydration which is overhydrating without supplementing with the proper amount of electrolytes.

This overhydration results in a condition called hyponatremia which can be very dangerous. We want to avoid it at all costs.

Related: 18 Healthy Whole Food Alternatives To Gels For Runners

Fluid And Electrolytes A Runners Guide


Hyponatremia is the result of overhydration. Here, the body’s sodium concentration in the blood dilutes and becomes too low. Without the proper amount of sodium, the body becomes unable to regulate the amount of water around the cells, which in turn, causes them to swell. 

This has been seen in runners in various marathons, especially when the weather is hotter than expected. In an attempt to stay hydrated, some drink in excess which can provoke this outcome. 

Some of the signs of hyponatremia are nausea, vomiting, headache, confusion, fatigue, and muscle cramps. As you can see, most of these symptoms are also present in dehydration. If the case becomes more serious, it can result in seizures or a coma. 

As runners, the more significant risk is dehydration. However, hyponatremia is a potential issue and should be known to all in hopes of avoiding it.

How Much Fluid and Electrolytes Should A Runner Consume?

This is a tricky one, as while there is a way to measure fluid loss, it’s not that easy to measure electrolytes. So instead, to ensure you are consuming enough fluids during your runs, conduct the following sweat test.

Fluid And Electrolytes A Runners Guide

The Sweat Test: How To Calculate Fluid Loss

1. Weigh yourself with no clothes.

2. Run for one hour at your specific race pace.

Note: During your run, do not consume or expel any liquid…so in simpler terms: no drinking or peeing! This will throw off your calculation.

3. After your one-hour run, take off your shoes, clothes, and if necessary, wring out your sopping wet hair.

4. Weigh yourself again.

Now let’s calculate our results!

Take your pre-run weight and subtract your post-run weight. The outcome will be the amount you sweat per hour while you run. Let’s take a look at examples using kilos and pounds: 


50 kilos (pre-run weight) – 48.5 kilos (post-run weight) = 1.5 kilos = 1.5 liters per hour


125 pounds (pre-run weight) – 122 pounds (post-run weight) = 3 pounds = 48 ounces per hour

The goal is to replenish at least 80% of your fluid loss per hour while you run.

Fluid And Electrolytes A Runners Guide

Measuring Electrolyte Loss

As mentioned, there isn’t really a home test like the sweat test to measure the number of electrolytes you are expelling per hour. Therefore, trial and error will be the best way to go.

You’ll know you have found your balance when you do not experience cramping or other dehydration symptoms during a race or run. You’ll likely see improvements in your performance and recovery, too.

To start, use sources of fluid and electrolytes such as sports hydration drinks during your next run for over an hour. This will help significantly replenish the electrolytes you are expelling when you sweat.

You can choose drinks with or without carbohydrates, depending on your needs. Sports drinks that contain carbohydrates help to increase water absorption into the bloodstream. You also won’t have to consume many products such as gels or gummies, as your sugar will be coming straight from your hydration. 

If you try this out and are still cramping or feeling signs of dehydration, you may need to include additional sources of electrolytes, such as salt pills in your regiment. The recommended dosage will depend on you and your specific needs, so start with one, and take it from there. 

Most sports salt pill supplements contain sodium, potassium, calcium, and magnesium – precisely what we need to get back into our system.

Fluid And Electrolytes A Runners Guide

Another option is to make your own DIY electrolyte drink by mixing together your favorite fruits and veggies that are high in electrolytes. Take a peek at this recipe!

Other Factors That Affect Fluid and Electrolyte Levels

There will be other factors that will affect the amount of fluid and electrolytes you will need, such as:

  • Weather: The hotter and more humid conditions you run in, the more you will sweat and, in turn, need to replenish with sources of electrolytes. 
  • Duration: The longer the run, the more you will need to replenish.
    • If your run is 30 minutes, you can get away with drinking before and after and not during. If you are running between 30- 60 minutes, water is just fine. If your run is over 60 minutes, it is a good idea to bring a sports drink or DIY electrolyte drink along to replenish during your workout. 
  • Intensity: The higher the intensity, the more you will sweat, and the more you will need to replenish your fluid and electrolytes.

5 Tips For Keeping A Good fluid And electrolyte balance

#1: Hydrate Regularly

Don’t just think about hydration when working out, but as a constant in your day-to-day life. Most of us will be able to count on 2 liters of water a day to ensure proper hydration, but some may need to add extra electrolytes to that fluid depending on specific needs.

fluid and electrolytes

#2: Hydrate Before You Run

Add around 500 ml of fluid to your pre-run snack about two hours before your run. Make it fruit juice for some added carbs and kill two birds with one stone!

#3: Hydrate During Your Runs

If your run is longer than 60 minutes, be sure and replenish 80% of your average fluid loss while running. This is especially important for high-intensity workouts, long runs, and races.

#4: Replenish Your Fluid and Electrolytes After Your Runs

Just because you drank before and during doesn’t mean you stop there. Replenish after your runs with a recovery drink, including the all-important electrolytes discussed. An all-around recovery will also include protein and carbohydrates to give you a complete restoration!

#5: Eat a Well-Balanced Diet

Eating a well-balanced diet, including water and electrolyte-filled foods, can help replenish needed fluid and electrolytes in the body. Let’s take a look at some great options: 

  • Fruit: Watermelon, strawberries, cantaloupe, peaches, and tomatoes 
  • Veggies: Cucumber, lettuce, spinach, kale, celery, zucchini, cauliflower and broccoli
  • Other: Soup, broth, and skim milk

From our daily hydration to our running-specific strategies, we need to take care of these details for the sake of our performance and, more importantly, our health. We want to run at our best and live our best lives, so let’s do everything we can to make that happen. 

Fluid And Electrolytes A Runners Guide

If you liked this article on fluid and electrolytes and want to delve even deeper into this topic, check out my ultramarathon nutrition guide here!

gels can be a great way to Replenish Fluid and Electrolytes – but only if taken Correctly . . .

Interested? Check out our article below explaining energy gels and how to take them.

Photo of author
Katelyn is an experienced ultra-marathoner and outdoor enthusiast with a passion for the trails. In the running community, she is known for her ear-to-ear smile, even under the toughest racing conditions. She is a UESCA-certified running coach and loves sharing her knowledge and experience to help people reach their goals and become the best runners they can be. Her biggest passion is to motivate others to hit the trails or road alongside her, have a blast, and run for fun!

2 thoughts on “Fluid And Electrolytes: A Complete Runner’s Guide”

  1. Hello,

    Thanks for the great article and content in general.

    I just have one note I noticed:

    50 kilos (pre-run weight) – 49.5 kilos (post-run weight) = 1.5 kilos

    where 1.5 should in fact be 0.5 because 50 – 49.5 = 0.5.

    Have a great day and keep running!




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