Are Isotonic Drinks Good for Running? Here's the Science

December 19, 2025 •

3 min read

According to a 2016 NCBI research paper, isotonic drinks may help athletes maintain fluid balance and increase muscle cell stability during exercise. This balanced composition is key to understanding if isotonic drinks are good for running, offering a strategic advantage for both hydration and energy replenishment.

Quick Summary

Isotonic drinks can be beneficial for runners during prolonged or intense exercise by providing quick hydration and energy. However, they are not necessary for shorter runs, where water is sufficient and avoids added sugars.

Key Points

Strategic Fuel: Isotonic drinks can be beneficial for runs lasting over 60 minutes or during high-intensity efforts, potentially providing carbohydrates and electrolytes.
Not for Every Run: For shorter or less intense runs, plain water is sufficient.
Balanced Absorption: Their balanced concentration can aid absorption of fluids and nutrients.
Electrolyte Replenishment: They can help replace key minerals lost through sweat.
Trial and Error: It is recommended to test different isotonic drinks during training to ensure tolerance before race day.
Homemade Alternative: A homemade isotonic drink can be created using water, fruit juice, sugar, and salt.

What Are Isotonic Drinks?

Isotonic drinks are formulated with a concentration of carbohydrates and electrolytes similar to the fluids in the human body, typically containing 4-8% carbohydrates. This composition can facilitate rapid absorption of fluids and nutrients.

The Benefits of Isotonic Drinks for Runners

For runners engaged in prolonged or intense efforts, isotonic drinks offer several potential advantages over plain water:

Rapid Rehydration: Aids fluid absorption.
Quick Energy Supply: Provides a rapid energy source.
Electrolyte Replenishment: Replaces electrolytes lost in sweat.
Prevention of Cramps: Can help prevent muscle cramps related to salt depletion.
Improved Endurance and Performance: Can enhance endurance and delay fatigue.

Isotonic vs. Hypotonic vs. Hypertonic: A Comparison

Choosing the right sports drink depends on your training needs and involves understanding the difference in osmolarity (solute concentration) compared to blood plasma. For a detailed comparison of isotonic, hypotonic, and hypertonic drinks, including their osmolarity, primary purpose, ideal use cases, and potential drawbacks, refer to {Link: NDL Pro Health ndlprohealth.com}.

When and How to Use Isotonic Drinks for Running

For most casual runners doing short, low-intensity runs (under 60 minutes), water is sufficient for hydration. Isotonic drinks are beneficial in specific situations:

During Long Runs: For runs over 60-90 minutes, when glycogen stores deplete, an isotonic drink helps maintain blood sugar and provides energy.
High-Intensity Intervals: During intense training, an isotonic drink provides a quick carbohydrate boost.
Hot or Humid Conditions: High sweat rates in hot weather increase electrolyte loss, making an isotonic drink helpful for replenishment.

Drink in small, regular sips (every 15-20 minutes) to avoid gastric distress. Always test new drinks during training before race day.

Potential Risks and Considerations

While beneficial for performance, overuse of isotonic drinks, particularly by inactive individuals or during short runs, can lead to weight gain due to high sugar content. The sugar and acid in commercial sports drinks can also harm dental enamel. Some individuals may experience stomach upset from the carbohydrate load. Excessive intake can also contribute to hyponatremia in extreme cases. Individual needs, sweat rate, and training intensity should guide intake.

Homemade Isotonic Drink Recipe

Making your own isotonic drink allows you to control ingredients and avoid additives.

How to Make Your Own Isotonic Mix

Ingredients: 1 litre water, 40-50g sugar or honey, a pinch of salt (approx. 1/4 tsp), and lemon or orange juice for flavor.
Instructions: Dissolve sugar and salt in a small amount of hot water. Add remaining cold water and juice. Chill before serving. Consume within 24 hours.

Conclusion: Are Isotonic Drinks Right for You?

For runners, the suitability of isotonic drinks depends on the run's duration, intensity, and conditions. For longer or more demanding efforts (over an hour), their carbohydrate and electrolyte content offers a performance advantage. For shorter, less intense runs, water is preferable, providing hydration without excess sugar and calories. Personalize your hydration based on your needs to effectively fuel and rehydrate for your running goals. Find more personalized hydration and fuelling advice here.

Scientific Basis for Use

The balanced osmolarity of isotonic drinks can aid absorption of water and nutrients into the bloodstream. Electrolytes help retain fluids and maintain balance for muscle and nerve function. Carbohydrates help sustain endurance, and electrolytes aid temperature regulation. This support is particularly valuable for endurance runners, especially in hot conditions with high fluid and salt losses.

Frequently Asked Questions

A runner should choose an isotonic drink over water for runs lasting more than 60-90 minutes, or during high-intensity sessions, especially in hot conditions. For shorter runs, water is generally adequate.

Isotonic drinks have a similar concentration of solutes to blood, offering a balance of hydration and energy. Hypotonic drinks are less concentrated, providing faster hydration but less energy, and are better suited for shorter efforts or light exercise in extreme heat.

Yes, some runners may experience stomach cramps, nausea, or other gastrointestinal discomfort if they consume isotonic drinks too quickly or in large volumes, especially if their stomach is sensitive to the high sugar content.

Most isotonic drinks typically contain electrolytes such as sodium, potassium, calcium, and magnesium, which are important for maintaining fluid balance, nerve transmission, and muscle function.

Yes, a homemade isotonic drink can be made by mixing water, a source of carbohydrates (like fruit juice or sugar), and a pinch of salt. This allows you to control the sugar and electrolyte levels to suit your needs.

No, an isotonic drink is not necessary for every run. For lower-intensity or shorter runs under 60 minutes, plain water is sufficient to meet your hydration needs.

Isotonic drinks can help prevent muscle cramps by replenishing the electrolytes, such as sodium and potassium, lost through sweat, which is important for muscle contraction.