How Much Water Should An Athlete Drink Each Day: Expert Recommended Hydration Guidelines

You've probably seen runners and other athletes walking around with gallon-sized water bottles, electrolyte tablets, sports drinks, and even pickle juice shots, all in the name of "staying hydrated." And while you know drinking water is important, you may be wondering if the guidelines are really all that different for an active individual and someone who's more sedentary.

The short answer is "Yes," but it gets a little more complicated, because there's no "one size fits all" rule for how much water each athlete should drink. That's why it's so important to be cognizant of the guidelines set forth by organizations like the American College of Sports Medicine (ACSM), International Society of Sports Nutrition (ISSN), as well as leading sports medicine physicians.

These guidelines help outline the measures an athlete should take to stay hydrated based on personal activity level and needs, with the understanding that the "rules" can change from day-to-day and person-to-person. Here is what you need to know about hydration for athletes including when to hydrate and how to calculate hydration.

Hydration Guidelines for Athletes

Here's the thing about being human—everyone's different. While the human body is made up of almost 60% water, an individual's water content varies based on factors like age, sex, and body composition.

Likewise, every individual has a different sweat rate which leads to different levels of fluid loss during activity. Not to mention, the intensity, environment, and type of exercise an individual engages in all lead to a different level of fluid loss. Someone lifting weights for 1 hour in an air conditioned gym isn't likely to lose nearly as much water and electrolyte content as someone running a marathon in hot conditions.

"There is no formula for what an ideal amount of fluid consumption is," says M. Ramin Modabber, MD, orthopedic surgeon at Cedars-Sinai Kerlan-Jobe Insitute in Los Angeles and Medical Director and Chief Medical Officer for the Amgen Tour of California. "Athletes demonstrate a wide variability in baseline physiology, overall health status, medical conditions, injuries, training regimens, and other factors."

Also, endurance events vary in duration and intensity of activity, temperature, humidity, access to fluids, and more, so each of these can play a role, Dr. Modabber adds. So, the overall picture must be considered. This is why hydration guidelines for athletes rely on individual measures so that you can make relevant, individual decisions regarding water and electrolyte intake.

Specifically, both the ISSN and ACSM break down an athlete's hydration guidelines into three separate categories including pre-hydration (consuming fluids before exercise), fluid intake during exercise, and rehydration post-exercise. By paying attention to all three categories, you're reducing the likelihood of experiencing dehydration during or following an athletic event which could lead to reduced performance or related health concerns.

To determine your own needs, there are two primary ways to gauge hydration status. These include the pee test as well as pre- and post-exercise weigh-ins.

Using these two measures, you can apply the other guidelines for fluid intake set out by the ACSM and ISSN to help you stay well-hydrated for exercise performance and health. Just keep in mind that for athletes and active individuals, thirst isn't an appropriate way to gauge whether you should be consuming more fluids. Thirst is a late response to dehydration, especially for the elderly.

Pee Test

The color of your urine is a good indicator of your hydration status. If you're peeing frequently and the color is clear or almost-clear, you're well-hydrated. If you're not peeing regularly and, when you do, it's dark or a highly-concentrated yellow, you're most assuredly at least somewhat dehydrated.

It's particularly important to be well-hydrated before starting exercise, which is why pre-hydration is critical to performance. It's also an important part of the next step—the pre-exercise weigh-in—as this helps determine post-exercise fluid intake needs.

Pre- and Post-Exercise Weigh-Ins

If you're well-hydrated before exercise, weighing in before your workout or event, and then again after your workout, enables you to use the change in weight to determine your rehydration needs following your workout or event.

Calculating Recommended Water Intake

First and foremost, it's important to remember that the water intake needs for athletes exceed those of an inactive person. And the needs you have on days you exercise will exceed those on days you don't.

By getting a general idea of what you should be drinking on a day when you're not exercising, you can then add to the baseline amount of water for the days you're breaking a sweat.

According to research on fluid intake requirements, the average amount of fluids that a man needs to consume to maintain hydration levels with minimal activity is about 3.7 liters per day, with women needing slightly less—closer to 2.7 liters per day. The requirements come from both food and beverages with 20% of these fluids coming from foods, while the other 80% comes from water and other hydrating liquids.

Of course these numbers are averages, and don't account for personal differences or environmental factors. But they should be the baseline levels of water consumption to shoot for, before adjusting for exercise.

Then, when calculating your specific water-intake needs, you should use the pee test and the pre- and post-workout weigh-ins to get a good idea of how much additional water you should be drinking.

When to Hydrate

If it is tough to determine a strict set of fluid intake parameters. But it can be even more challenging to determine if you're drinking enough fluids based on your fitness routine.

By following standard pre-hydration guidelines, and using a combination of the pee test and exercise weigh-ins, you can get a pretty good feel for the amounts of fluid you should be consuming before, during, and after exercise. Then, based on specific conditions (like a very hot day or a particularly strenuous workout), you can make adjustments, as needed.

Here are some additional guidelines on when and how to hydrate.

Pre-Hydration Before Exercise

The ACSM's guidelines are fairly general when it comes to drinking fluids before exercise. They simply state that athletes should start drinking small amounts of water at least 4 hours before a bout of exercise with the goal of reaching "euhydration," or being appropriately hydrated, before exercise begins.

This amounts to about 5 to 7 milliliters per kilogram of weight. If you are dehydrated, you may need another 3 to 5 milliliters per kilogram of weight two hours prior to the event. The recommendation goes as far as suggesting sodium-containing beverages to increase fluid intake and retention.

The ISSN offers slightly more specific recommendations, suggesting that athletes consume 500 milliliters of water or sports drink the night before a competition, 500 milliliters upon waking, and another 400 to 600 milliliters roughly 30 minutes before exercise commences. This, along with a normal eating schedule, should help you achieve optimal pre-exercise hydration.

Hydration During Exercise

Both the ISSN and ACSM emphasize that the point of hydrating during exercise is to prevent substantial fluid loss (>2% body weight loss), which can lead to subpar performance or potential health concerns. The problem is that based on activity, duration, intensity, and individual sweat rates and fluid needs, it's nearly impossible to offer a clear guideline.

Both organizations note that sweat rates for prolonged exercise can vary from 0.5 liters to 2 liters per hour, and that athletes should try to "keep up with" losses by consuming liquids steadily throughout exercise every 15 to 20 minutes.

The ACSM suggests using pre- and post-workout weigh-ins to craft a personalized hydration plan over time based on your own typical fluid losses. For instance, if you weigh 2.2 pounds less after a workout than when you started, that's the equivalent to a 1 liter loss of fluids, so the next time you perform a similar workout, you should plan on consuming a total of 1 liter of fluids over the course of your workout period.

Another starting point recommendation is consuming 0.4 to 0.8 liters every hour for marathon runners or exercisers that are going to be working out longer than 1 hour. If you are running smaller bouts, closer to 0.4 liters per hour is recommended. ACSM also recommends consuming 30 to 60 grams of carbohydrates (not to exceed 80 grams) per hour along with some sodium and potassium.

The ISSN, on the other hand, states that athletes should plan to consume roughly 12 to 16 ounces of fluids every 5 to 15 minutes over the course of a workout. The fluids should contain a 6 to 8% carbohydrate solution with 300 to 600 milligrams of sodium.

Those performing more intense workouts for longer periods of time, especially in hot or humid environments should plan on drinking more fluids more frequently, with those performing less intense workouts in less challenging environments skewing toward less fluid consumption on a less frequent schedule.

Rehydration Post Exercise

Post-exercise rehydration comes down to replacing the fluids and electrolytes lost during exercise. This is where the pre- and post-exercise weigh-ins can come in handy. According to the ISSN, for every pound lost during exercise, you should consume 3 cups of water.

This doesn't need to be done all at once. Rather, it can be done steadily following your workout, with the goal of completing consumption before your next bout of exercise to ensure you've appropriately rehydrated.

The ACSM notes that if time permits, sticking to a normal eating and drinking schedule after your workout should be enough to restore euhydration. But if you have to rehydrate quickly (say, in between basketball games during a tournament), drinking about 1.5 liters for every kilogram of body weight lost before you exercise should help you get there.

"Thirst is not a dehydration barometer. Just because you’re not thirsty doesn’t mean you’re hydrated," emphasizes Rathna Nuti, MD, board-certified sports medicine doctor and medical volunteer for the US Olympic & Paralympic Committee, and assistant team physician for the Dallas Stars National Hockey League Team.

This is particularly true during long athletic events, where your fluid loss through sweat may outpace your body's response to flag for thirst.

When Should You Drink Water vs. Electrolytes

Water is an excellent drink for rehydration, but you don't just lose water as you sweat—you lose electrolytes, too. And when you've participated in a particularly sweaty workout, or an extended workout in hot weather, you may end up with an electrolyte imbalance.

This imbalance needs to be restored to ensure your body recovers appropriately. In the following instances listed below, you should consider using fluids with electrolytes mixed in to help rehydrate.

Exercise for More than 90 Minutes

When you exercise for longer than 90 minutes, you're placing additional stress on your systems, and you're losing a significant amount of water and electrolytes through sweat. For shorter workouts, the electrolyte loss is unlikely to be significant enough to impact performance.

You can restore the losses more easily following your workout by consuming water and a normal diet. But when you start logging those extra-long workouts, your body is likely to need a boost of electrolytes in addition to water alone.

Exercising in Warm Weather

When you exercise in heat, your body uses it's natural cooling system—sweat—to keep your body temperature from rising. That means the workouts you do on hot days result in greater fluid and electrolyte loss.

If you're exercising in the heat, particularly if you're exercising for longer than 60 to 90 minutes, it is best to add some carbohydrates and electrolytes to your fluid consumption to prevent dehydration and immunosuppressive effects of intense exercise. Doing so, will ensure you keep your system hydrated and balanced.

Exercising at Altitude

You may not have ever thought about it, but exercising at higher altitudes results in more fluid loss, not only through sweat loss (which remains similar to the loss you might experience at sea level), but through increased loss of respiratory water.

This loss occurs because the air is thinner at higher altitudes and you have to breath at a faster rate to intake the same level of oxygen as you would at lower altitudes. The result is that you expire more water into the air.

Plus, the physiological changes that take place when exposed to high altitudes for a brief period of time (when you haven't acclimated to the environment), also affect how your body responds to exercise. All of these factors combined add up to a situation where you might benefit from electrolyte intake as you rehydrate.

Athletes Prone to Experiencing Fluid losses

Finally, any athlete who is experiencing greater fluid losses for any other reason should also consider using an electrolyte-enhanced fluid as part of the rehydration plan. This includes athletes with injuries, medical conditions, or illnesses—particularly if diarrhea or vomiting are involved.

It is particularly important to pay attention to electrolyte balance in any situation where dehydration is more likely to occur with exercise.

"When it comes to replacing the body's storage of electrolytes, there are plenty of sports drinks, potions, and powders on the market today that claim to do just that," says Dr. Modabber. "But not all of them are created equal."

A Word From Verywell

Athletes need to be particularly conscientious about water intake levels, as well as electrolyte balance in order to help prevent dehydration. By paying attention to the color and concentration of your urine, and doing pre- and post-workout weigh-ins, you can develop a pretty good idea of your personal water intake needs.

But, if you're concerned about dehydration or you're unsure whether you're drinking enough water, consult with a sports dietitian or a healthcare provider that specializes in sports medicine to discuss whether you can get a more personalized assessment.