Hydration for Runners

Written by Health Loft
Published on October 17, 2023
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What is hydration?

Hydration before, during, and after a run is essential because our body is made up of about 45-75% water. As our muscles are working harder during a workout, we need more water and hydration to keep them functioning optimally and to avoid injury. For physically active people, it can be hard to keep our bodies in an optimal hydrated state due to large volumes of water lost through sweat and the lack of thirst during exercise.


Dehydration can negatively impact running and exercise by causing early fatigue, leading to a decrease in performance, recovery, mental awareness, stamina and can even lead to injury or heat illnesses. Some signs of dehydration may include fatigue, headache, dizziness, thirst, weakness, chills and dark colored urine. Losing as little as 1-2% of your body weight during your workout can significantly decrease your aerobic performance. For example, if you are a 150-pound runner and you lose more than 1.5-3 pounds during a workout, you are at significantly greater risk for severely reduced mental and physical performance. Recovering from moderate to severe dehydration is not a fast process.  To fully recover it can take up to 3 days for the body to to effectively rehydrate. Being proactive about your hydration is key.

Hydration and Injury Prevention

When our muscles become dehydrated, they are more susceptible to injury and tears. As our body loses water through sweat during exercise, we need to replenish the water losses to keep our total body water in balance. Strains, sprains and muscle cramping are common ailments from becoming dehydrated, which can negatively affect our performance and ability to train.

Being Proactive About Hydration (Preventing Dehydration)

The only way to prevent dehydration is to stay on top of your fluid intake before, during and after running! Always make sure you start your workout in a hydrated state. The simplest way to monitor your hydration is to check your urine color. Your urine should be a pale yellow color, similar to the color of lemonade. By hydrating a few hours prior to the start of your run, this will allow sufficient time for your urine output to return to normal before hitting the road. Consuming beverages with sodium and/or small amounts of salted snacks can help stimulate thirst and retain the fluids you consumed prior to exercise. As a rule of thumb, consume half your weight in ounces of water each day. For example, if you are a 150-pound runner, your daily water goal is 75 ounces per day. BUT don’t forget, if you are running or exercising, you will need more water due to losing fluids through sweat.

Assessing Hydration Status

A more thorough way to assess your own hydration status is to:

  1. Weigh yourself without clothes before a workout
  2. Workout for 1 hour (note how many ounces of water consumed during this time and how many ounces of water excreted through urine)
  3. Weigh yourself without clothing after a workout.

To find sweat rate, use the following equation:

Your sweat rate will tell you how many liters of water you lose in 1 hour of working out. This will help you know how many ounces (34 ounces = 1 liter!) of water you need to be consuming at minimum per hour to stay hydrated based on your sweat rate. If you are not taking in this much fluid during your workout to keep up with your sweat rate, it will be important to focus on re-hydration after.

Role of Electrolytes in Staying Hydrated

Sweat is primarily made up of water but includes electrolytes as well. When we are losing fluids through sweat, we lose electrolytes that are essential to keeping our body hydrated and our muscles functioning. Electrolytes in our sweat include sodium, potassium, magnesium, chloride and calcium. Sodium, potassium and chloride are the most abundant in our sweat and all work together to keep our body in a hydrated state. Magnesium and calcium are also essential for hydration because they keep our muscles moving and working properly. Sodium is the most abundant electrolyte in our sweat, and not only keeps us hydrated throughout activity by retaining water in our body, but is also important in stimulating complete re-hydration after activity. It is also shown that drinks containing sodium increase the desire to drink fluids and are more pleasant to taste.

Sources of Electrolytes

Sports drinks like Gatorade and Powerade are designed to have both electrolytes and carbohydrates to keep you hydrated and fueled during a run. Carbohydrates provide glucose for quick energy for your body to use during activity. Though sports drinks are a viable option to hydrate and keep your electrolyte intake up, you can also look to food to do the same. If you know you are a salty sweater, it may be  beneficial to incorporate salty snacks before and after a run to help retain fluid in your body. Some examples of sodium rich foods include salted nuts, pretzels and crackers. Potassium rich foods include bananas, avocado, potatoes and dark leafy greens. Foods high in magnesium include seeds, nuts, spinach and beans. Foods rich in calcium include yogurt, milk, almonds and broccoli. Eating a variety of these foods will ensure you are getting enough total electrolytes throughout the day. When using foods as your source of electrolytes, be sure to find the best options that work for you. One snack might be perfect for one athlete, and not sit well for another. Try different pre-run snacks before a shorter run to see what works and what energizes you.

How do I know if I need electrolytes?

If you know that you are a salty sweater meaning you can taste it, feel it or even see it on your skin, then it is important to keep a consistent intake of electrolytes, along with water, to avoid becoming severely dehydrated during a run. Amounts of sodium and electrolytes depend on your sweat rate and can vary depending on the activity, intensity level, and climate. The hotter and more humid the climate, the more you are likely to sweat and lose electrolytes. Sodium intake of 1000 mg per hour is recommended during prolonged exercise where heavy sweat is expected. For example, a small bag of pretzels can contain 400-500 mg of sodium and provides carbohydrates too. Other options could be electrolyte packets such as Drip Drop or Liquid I.V., which contain 500-600 mg of sodium. Pairing the pretzels and electrolyte packet together will help you stay fueled during your run while also providing you with the electrolytes and hydration you need to keep going.

When are sports drinks necessary?

Sports drinks have their advantages over plain water when it comes to performance. Sports drinks help replace electrolytes lost in sweat. They also provide a source of carbohydrates, which provides fuel for active muscles to help us keep going during a run. If you are doing exercise longer than an hour, you may want to consider incorporating a sports drink. Anything under an hour, depending on your sweat rate, you may be able to get by with just plain water.

How much should I be drinking before, during and after a run?

Remember, it is important to ensure you are starting exercise in a hydrated state. Consume 16-20 ounces of water at least 4 hours before a run to ensure you are hydrated. 15-30 minutes before, aim for 8-12 ounces of water to top off your hydration tank. During a run, try to take in small amounts of fluid (3-8 ounces) every 15-20 minutes to combat dehydration. For runs over an hour, it may be important for you to incorporate a sports drink instead of plain water to ensure you are getting in electrolytes and some carbohydrates too. Having small handheld water bottles or a belt with water bottles will allow you to utilize both electrolytes and plain water during your runs. After a run, re-hydration is key! Plain water is a good thirst quencher, but may not be enough to fully re-hydrate due to the lack of electrolytes. Re-hydrating initially after a workout with a sports drink is ideal to refuel your body with fluids, sodium and carbohydrates. Continuing to re-hydrate with plain water is important as you may not need the sugar and electrolytes hours after your workout. To ensure total re-hydration, aim for 125-150% of weight lost for re-hydration. For example, if you lose 1 pound (16 ounces) during your workout, aim for 20-24 ounces of fluids after exercise. Be sure to monitor your urine as well and aim for a pale yellow color!

If you want a personalized hydration or nutrition plan for your running and fitness goals, you can talk to a Health Loft dietitian in Chicago, IL (virtually via our telehealth platform or in person) by calling us at (312) 374-5399 or by scheduling an appointment online. For more tips and fun facts to also check out our FacebookInstagram, and Twitter pages for more articles on nutrition, physical therapy, and exercise!




Submitted by Laura Asbury
Edited by Alexander Franz
Reviewed by Morgan Murdock, RD






Karpinski, C. and Rosenbloom, C., 2017. Sports Nutrition A Handbook for Professionals. Pp.107-129.

Swaka, M., Burke, L., Eichner, R., Maughan, R., Montain, S. and Stachenfield, N., 2007. Exercise and Fluid Replacement. Medicine & Science in Sports & Exercise, 39(2), pp.377-390.

Thomas, D., Erdman, K. and Burke, L., 2016. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Journal of the Academy of Nutrition and Dietetics, 116(3), pp.501-528.

Sherman, T., Siekaniec, C. and Johnson, S., 2020. What’s In Your Sweat. Sportsrd.org. Available at: <https://www.sportsrd.org/wp-content/uploads/2018/11/Whats-In-Your-Sweat.pdf>

2020. Hydrate Early And Often. Available at: https://www.sportsrd.org/wp-content/uploads/2016/01/Hydration-Screen-Shot-.png

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