What Is the Best Hydration Drink Before a Marathon?

November 21, 2025 •

5 min read

Dehydration leading to just a 2% body mass loss can reduce running performance by 10-20%. Knowing what is the best hydration drink before a marathon is therefore a critical component of race preparation for any endurance athlete aiming for peak performance and successful completion.

Quick Summary

This guide details the optimal hydration strategy for your marathon, including the best types of drinks, correct timing, and personalized approaches to maximize endurance and avoid common pitfalls like hyponatremia.

Key Points

Start Hydrated: Begin hydrating consistently 48-72 hours before the race to preload your system and avoid starting with a deficit.
Choose Electrolytes: Opt for an electrolyte-rich drink over plain water, especially in the 24 hours leading up to the race, to aid fluid retention and prevent hyponatremia.
Time Your Intake: Drink a significant portion of fluid (16-20 oz) 2-3 hours before the start, allowing time for absorption and bathroom breaks.
Practice in Training: Experiment with different hydration drink types and schedules during long training runs to find what your body tolerates best.
Monitor Your Sweat Rate: Personalize your fluid intake by weighing yourself before and after runs to determine your individual sweat loss and replacement needs.
Consider the Weather: Adjust your hydration needs based on temperature and humidity, increasing fluid and electrolyte intake in hotter conditions.

The Science Behind Pre-Race Hydration

Proper hydration for a marathon begins long before race day. It is a multi-day process focused on ensuring your body's fluid and electrolyte levels are optimized. The goal is not just to replace lost water but to start the race with sufficient fluid volume in your blood plasma, which enhances thermoregulation and oxygen delivery to your working muscles.

Why Plain Water Isn't Enough

For runs under an hour, plain water is often sufficient for hydration. However, during the intense, prolonged effort of a marathon, your body loses more than just water through sweat. Essential minerals, known as electrolytes—including sodium, potassium, and magnesium—are depleted. Consuming large volumes of plain water in the lead-up to a race can actually be detrimental, as it can dilute your body's sodium levels and increase the risk of a dangerous condition called hyponatremia, or water intoxication.

The Critical Role of Electrolytes

Electrolytes are crucial for proper nerve and muscle function, fluid balance, and blood pressure regulation. Sodium, in particular, is vital for retaining fluids and maintaining blood volume. The best hydration drink before a marathon should contain a strategic blend of electrolytes to help your body absorb and retain the fluid you're consuming. The amount of sodium required varies significantly among individuals, as some runners are "salty sweaters" who lose more sodium than others.

Types of Pre-Marathon Hydration Drinks

Choosing the right drink is a personal process that requires testing during your training. Below is a comparison to help guide your decision.


Drink Type	Composition	Best For	Considerations
Plain Water	H2O only	Short, low-intensity runs (<1 hour).	Lacks electrolytes for longer runs; risk of hyponatremia if overconsumed.
Isotonic Sports Drinks	Water, carbs (6-8%), electrolytes	Moderate-to-high intensity runs >60 mins.	Sugar content can be high; may cause GI distress for some; sodium levels can vary.
High-Sodium Electrolyte Mix	Higher sodium content, some carbs	Pre-loading, hot/humid weather, or heavy sweaters.	Can taste salty; higher cost than DIY options.

Commercial Electrolyte Drinks

Many athletes turn to commercial products for their convenience and balanced formulas. Brands like Nuun, Tailwind Nutrition, Skratch Labs, and LMNT offer different formulations suitable for various needs. Nuun Sport tablets are popular for their low-carb profile, ideal for pre-race hydration where fuel is not the primary focus. For heavy sweaters, brands like LMNT offer a high-sodium solution. Other mixes, like Skratch Labs, use real fruit for flavoring and also provide carbs for energy. Testing these during training is crucial to find what your stomach tolerates best.

DIY Homemade Hydration Drinks

For those who prefer a more natural or cost-effective alternative, a homemade hydration drink can be a great option. Simple recipes can provide a good balance of carbohydrates and electrolytes.

Coconut Water Mix: Combine 1.5 cups unsweetened coconut water (for potassium) with 2 cups of water, a squeeze of lemon juice, and ¼ teaspoon of salt. This creates a potassium-rich electrolyte drink with a mild flavor.
Juice and Salt Mix: Mix 2 cups of water with ½ cup of your preferred fruit juice (e.g., orange or grape juice) and ¼ teaspoon of salt. The juice provides simple carbohydrates for energy, while the salt replenishes sodium. Ensure you have tested any homemade recipes extensively during long training runs to avoid race day gastric issues.

Your Race Week Hydration Strategy

Proper hydration isn't just about what you drink on race morning. A successful strategy starts days in advance.

48-72 Hours Before: Focus on consistent, sufficient hydration throughout the day. This is also when you should be increasing your carbohydrate intake as part of carb-loading, and drinking more fluid will naturally accompany this process. Avoid alcohol, which is dehydrating.
The Day Before: Maintain a steady intake of fluids. Sip regularly throughout the day and avoid large gulps that can lead to excessive urination. Aim for around 2-3 liters of fluid, adjusted for sweat loss.
Race Morning: Drink about 16 ounces (500ml) of an electrolyte drink or water with your pre-race breakfast, 2-3 hours before the start. This allows time for absorption and to use the restroom. Take a final small sip of 6-8 ounces about 15 minutes before the race.

Personalizing Your Hydration Plan

Monitoring Your Sweat Rate

One of the most effective ways to personalize your hydration is by understanding your unique sweat rate. Weigh yourself (naked) before and after a long training run. For every pound of body weight lost, aim to consume 16-24 ounces of fluid to replace the loss. This helps you understand how much you need to drink during the race itself.

Consider the Conditions

Environmental factors like temperature and humidity significantly affect your sweat rate and overall fluid needs. In hot and humid conditions, your fluid and electrolyte intake needs to be higher. In cooler weather, your needs might be lower, but strategic hydration is still important to prevent performance decline.

Conclusion

Ultimately, there is no single best hydration drink for everyone before a marathon. The best approach is a personalized strategy developed and tested during training. It involves consistently hydrating in the days leading up to the race, choosing an electrolyte-rich drink to maximize fluid absorption, and timing your intake correctly on race morning. By paying close attention to your body's specific needs and the race day conditions, you can confidently arrive at the starting line primed for your best performance.

For further reading on the relationship between hydration and performance, you may find the following clinical study insightful: Influence of Hydration on Physiological Function and Performance During Trail Running in the Heat.

Summary of Race Day Hydration Strategy

Start Hydrated: Begin hydration days before the race, not just on race morning, by consistently sipping water and electrolyte drinks.
Electrolytes are Key: For runs over an hour, or in hot conditions, electrolytes are more effective than plain water at promoting fluid retention and preventing hyponatremia.
Commercial vs. Homemade: Popular commercial options like Nuun and Tailwind offer balanced formulas, while homemade drinks with coconut water or juice provide a natural alternative; test all options in training.
Timing is Everything: Drink a larger volume (16-20oz) 2-3 hours pre-race to allow for absorption, and smaller sips (6-8oz) 15 minutes before the start.
Listen to Your Body: Monitor your personal sweat rate and adjust your hydration plan based on environmental conditions and how you feel, practicing your strategy in training to avoid surprises.

Frequently Asked Questions

For marathons and long-distance running, an electrolyte-enhanced sports drink is generally better than plain water. It helps replenish essential minerals like sodium lost through sweat, aids in fluid retention, and often provides carbohydrates for energy.

You should aim to finish drinking most of your pre-race fluid, such as 16-20 ounces of water or a sports drink, about 2-3 hours before the race starts. This allows time for your body to absorb it and for you to use the restroom. A final, smaller sip of 6-8 ounces can be taken 15 minutes before the gun.

You may be a 'salty sweater' if you notice visible white, salty residue on your running clothes or skin after a run, or if your sweat stings your eyes. If so, you will need a drink with a higher sodium concentration.

Hyponatremia is a dangerous condition of low blood sodium caused by over-drinking plain water, which dilutes the body's sodium levels. You can avoid it by choosing an electrolyte drink over plain water, especially for long distances, and by drinking to thirst rather than forcing excessive intake.

Yes, you can make a homemade hydration drink using ingredients like coconut water, fruit juice, salt, and water. Just ensure you test your recipe thoroughly during training runs to avoid any gastric distress on race day.

While many sports drinks contain carbohydrates, you should primarily focus on hydrating and consuming electrolytes in the hours before the race. Most serious carb-loading occurs in the 48-72 hours prior to the race, with the extra water you drink during that period aiding the process.

For runners who are accustomed to caffeine, a small to moderate amount can be beneficial for performance. Many electrolyte mixes and sports drinks offer a caffeinated version. However, if you are not used to it, avoid it on race day as it can cause stomach upset.