Hydration, Sodium, Potassium and Exercise: What You Need to Know

Delve into hydration dynamics during exercise, exploring the roles of sodium and potassium to uncover strategies for peak performance.

Perrin Braun
By Perrin Braun
Lucia Gcingca
Edited by Lucia Gcingca

Published March 6, 2024.

A woman drinking water from a bottle.

What’s a small thing you can do that can have a big effect on your performance? Drink enough water. Our bodies are mostly comprised of fluid, which means that every cell, tissue, and organ needs enough water to function. While plain H20 is the most important part of hydration, you also need electrolytes like potassium and sodium to perform at your best.

Why should you pay attention to hydration?

Hydration is necessary to maintain peak performance. Water regulates your body temperature, lubricates your joints, and transports nutrients throughout your body. [1] Staying hydrated is particularly important during exercise because you lose water through sweat.

The longer and more intensely you work out, the more necessary it becomes to get fluid into your body. [2] When you don’t replenish your fluids, it becomes harder for your heart to circulate blood.  A decrease in blood and plasma volume can contribute to muscle cramps, dizziness, fatigue, heat stroke, and heat exhaustion.

Electrolytes: Potassium and sodium for hydration

In addition to water, your body loses electrolytes when it sweats. Chloride, potassium, and sodium are major electrolytes, which are minerals in your blood, urine, and bodily fluids that contain an electric charge. Your body’s cells use electrolytes to carry electrical impulses that help your cells communicate with each other and give you the ability to taste, see, smell, touch, and hear. 

InsideTracker measures potassium and sodium in your blood to help you maintain your well-being and reach your personal fitness potential.

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Hydration strategies for athletes

For athletes, the right amount of water is pivotal but varies based on exercise intensity, duration, and sweat levels. Assessing your hydration status is crucial, and there are effective methods to ensure you're on track.

Monitoring hydration levels

One method involves observing your urine. Light-colored urine indicates sufficient hydration, while dark and concentrated urine may signal a need for increased water intake.

Additionally, tracking your weight before and after workouts provides tangible evidence, as immediate post-workout weight loss often points to fluid reduction.

American College of Sports Medicine guidelines

During the initial exercise hour, following the American College of Sports Medicine (ACSM) guidelines is a common practice among athletes:

  • Pre-exercise (4 hours before): Consume 2-3 milliliters (mL) of water or sports drinks per pound (lb) of body weight. For instance, a 150-lb athlete should aim for 300-450 mL (10-15 ounces) of liquid.

  • During exercise: Integrate approximately 8 oz of fluid every 15 minutes to counteract dehydration caused by sweating.

  • Post-exercise rehydration: After your workout, aim for 16-24 fl oz of fluid for every pound of body weight lost during exercise. This replenishment restores hydration levels and supports efficient recovery. [3]

Note: While the ACSM guidelines serve as a foundation, athletes often adjust their water intake based on individual preferences and needs. This flexibility allows athletes to tailor their hydration strategies for optimal performance.

» Learn more about how much water you should be drinking during exercise

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Why is sodium important for hydration?

Many people associate sodium with high blood pressure, heart disease, and canned foods, but it serves important functions in keeping your body healthy:

  • Maintains fluid balance in your cells
  • Helps to transmit nerve impulses throughout your body
  • Helps muscles contract and relax [4]

Signs of sodium deficiency

Because sodium is found in so many foods, it’s fairly uncommon to develop a sodium deficiency unless you’re having excessive vomiting or diarrhea. If you’re losing a lot of water, you’re probably also losing a lot of sodium. Symptoms of a sodium deficiency include:

  • Fatigue
  • Dizziness
  • Nausea
  • Muscle cramps
  • Inability to concentrate

Low levels of sodium can lead to hyponatremia!

Drinking too much fluid, especially plain water, can result in a dangerous condition in which there isn't enough sodium in your body fluids. If the deficiency really becomes serious, the body can go into shock, and the circulatory system can collapse. 

Excess sodium

Conversely, if our diets contain too much sodium, our body tissues tend to retain water. For reference, the 2012 American Heart Association recommended that people consume no more than 1,500 milligrams of sodium a day—just a bit more than 1/2 teaspoon of salt. [5] For comparison, a medium order of fast-food French fries contains about 260 milligrams of sodium. 

A recent study reported that Americans are consuming even more sodium—8% more in 2010 than in 2001. [6] Consuming too much salt can cause the kidneys to retain water, which can sometimes result in increased blood pressure, stroke, and heart disease. 

Why is potassium important for hydration?

In addition to helping to maintain a proper fluid balance in your body, potassium also performs the following functions:

  • Keeps the blood from clotting
  • Maintains the body’s pH balance
  • Carries nutrients to the cells
  • Protects the stomach lining from the damage that stomach acids could cause
  • Maintains healthy blood pressure
  • Promotes heart health
  • Preserves bone health [7]

Athletes and potassium intake

Athletes should be especially concerned with their potassium intake; potassium plays a role in the storage of carbohydrates to fuel your muscles. In addition, the frequency and degree to which your muscles contract depends heavily on having the right amount of potassium in the body.

When you don’t get enough potassium in your diet, or when the movement of potassium through the body is blocked, your nervous and muscular systems can become compromised. The Adequate Intake (AI) for potassium is 4.7 grams per day, but most Americans don’t consume enough potassium in their diets. [8]

» Discover how to make the most of your post-workout meal

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Tackling low potassium levels: Dietary insights

One reason for our low potassium levels is that Americans generally don’t eat enough fruits and vegetables. Bananas are a great source of potassium, which helps promote muscle recovery. You can also find the mineral in potassium-rich foods like:

  • Fish
  • Milk
  • Most meats
  • Sweet potatoes
  • Legumes - lima and kidney beans
  • Fresh fruits - especially citrus and melon
  • Vegetables - especially leafy greens and broccoli

Potassium's role in endurance

Because you lose potassium through sweat and urination, you need to be consuming these potassium-rich foods each day, especially if you’re an athlete. Low potassium levels can reduce your energy and endurance.

A recent Australian study with highly trained athletes showed that drinking a caffeinated beverage immediately before exercise can help to maintain adequate potassium levels in your blood and delay fatigue during your workout.

» Want to reach peak performance? Uncover what to eat before your workout

Checking your potassium and sodium levels

Your body will definitely let you know if you’re not hydrated. If you’ve been experiencing muscle cramping or high levels of thirst, get your potassium and sodium levels checked with InsideTracker.

Suppose your potassium or sodium levels aren't optimal. Then, InsideTracker will provide you with recommendations about what to change in your diet and introduce you to some new foods that can help.


[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2908954/

[2] https://pubmed.ncbi.nlm.nih.gov/11547892/

[3] https://pubmed.ncbi.nlm.nih.gov/9303999/

[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3951800/

[5] https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/sodium/how-much-sodium-should-i-eat-per-day

[6] https://www.researchgate.net/publication/352614118

[7] https://ods.od.nih.gov/factsheets/Potassium-Consumer/

[8] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6181280