Hydration 101 for Athletes
Why Hydration Matters
Water helps regulate our body temperature, maintain blood volume, deliver key nutrients to tissues throughout the body, and much more. Beyond maintaining life and basic function, water is also integral for supporting athletic performance. Dehydration can lead to poor thermoregulation, physical fatigue, impaired focus, and compromised performance (1,2). In this blog, we’ll tackle how to estimate your daily baseline fluid needs, how to meet additional hydration demands as an athlete, and what to consider when developing a hydration plan for activity.
Estimating Fluid Needs
Fluid needs, much like calorie needs, are highly individual. Age, physical activity level, body size, sweat rate, and environmental conditions all impact fluid needs. There’s no one-size-fits-all approach to figuring out how much fluid you need to consume daily. However, we’ll highlight three different methods below that you can use to get a general estimate of your baseline fluid needs, excluding additional fluid needed to support physical activity.
Option 1: As I shared in the Nutrition 101 blog, one of the simplest methods for estimating baseline fluid needs is to take your weight in pounds and divide by two, which provides an estimate of the number of ounces of fluid you should try to consume per day.
Weight (pounds) / 2 = # of ounces of fluid you should aim to drink per day
This method provides a decent starting point for baseline fluid needs, but may not work well for individuals who are not comfortable measuring or knowing their weight.
Option 2: Another simple equation that does not require knowing your weight is to drink approximately 1 milliliter of fluid per calorie consumed. For example, if you eat 2500 calories per day, you’d aim to drink about 2500 milliliters (or 2.5 liters) of fluid daily. There are limitations to this method. If you have very high caloric needs, this method may overestimate your fluid needs.
Option 3: If you want an even simpler starting point that doesn’t require any math, consider following The Dietary Reference Intakes (DRI). The DRI currently recommends 3.7 liters of total water per day for adult men and 2.7 liters of total water per day for adult women (3). This includes water from both food and beverages.
What Counts Toward Fluid Intake
When we’re estimating “fluid needs,” we’re considering all fluids that you’re consuming, not just water. Smoothies, soups, juices, sparkling water, sports drinks, dairy/non-dairy milks, coffee, tea, and moisture-rich foods all contribute to your daily fluid intake. Foods with a high water content include tomatoes, cucumbers, melon, celery, and other fruits and vegetables. Don’t worry about measuring how much water you get from food since it’s hard to quantify and the vast majority of your fluid intake will come from beverages. Instead, you can just think of moisture-rich foods as general hydration boosters.
Monitoring Hydration Status
If you don’t want to weigh yourself and don’t feel like doing any calculations or numeric tracking, you can monitor your thirst sensation and urine volume/color to get a sense of your hydration status. As a starting point, try paying extra attention to your thirst and respond accordingly by drinking when you feel thirsty. This might require extra intentionality if you’re used to going on “autopilot” throughout your busy day. It can be easy to ignore thirst signals when you are distracted by work, training, and other life demands. Remember that thirst can present in unique ways, such as dry mouth, headache, and fatigue. Keeping a water bottle near you at all times and setting reminders on your phone to consider a hydration break might help bring awareness to your thirst sensations if you feel like it’s something that you normally struggle to notice.
You can also monitor your urine frequency, volume, and color to gauge your hydration status. For most people, checking urine color is easier than keeping track of urine frequency and volume. Pale yellow urine, sometimes described as “light lemonade” or “pale straw” in color is usually a pretty good indicator of adequate hydration. If it's been a long time since you last urinated, and you're producing a small volume of dark yellow, possibly odorous urine, you're likely falling short on hydration. These indicators apply when you are awake and active, not when you’re sleeping overnight. It’s normal to sleep through the night without needing to wake to urinate and it’s likely that when you first urinate after waking up, your urine will appear darker and more concentrated. This is normal.
Keep in mind that some supplements and medications can alter urine color. For example, riboflavin, also known as vitamin B2, can lead to neon yellow/fluorescent colored urine that might lead you to believe that you’re dehydrated when you’re actually not.
Hydration Considerations for Athletes
Athletes can use the principles discussed above to help understand fluid needs, however, there are extra considerations to be aware of. As an athlete, you are likely sweating regularly. Sweat is composed of water and electrolytes (minerals), so you likely need to drink more total fluid than the average person to help replace what you are losing. This is particularly important for longer duration and/or higher intensity activity, where sweat losses tend to be higher. Sweat losses are also higher in hotter/more humid weather.
On top of your baseline fluid intake, consider the following pre, during, and post-training intake goals to make sure that you avoid dehydration and support your performance:
Pre-training - The goal is to start your training/event well hydrated. If you need concrete numbers, try starting with this: drink at least 16 ounces of fluid in the 2-3 hours leading up to start time, then top off hydration with another ~8 ounces of fluid in the hour leading up to start time (1).
During training - Intra activity needs are variable depending on the individual, activity type, and environmental conditions. Some people are fine just “drinking to thirst” (i.e. drinking only when you feel thirsty). Others benefit from some numeric guidelines and “programmed” or “scheduled” drinking. In general, athletes doing shorter-duration or stop-and-go sports (e.g. team sports, strength training) can often rely more on thirst, whereas athletes engaging in longer-duration endurance activities may benefit from more intentional hydration planning. Most athletes can cover hydration needs during activity by consuming ~13-27 ounces of fluid per hour as a starting range (1). However, there can be substantial variability across athletes and a personalized hydration plan based on sweat rate is more ideal (4). Whatever your fluid goal, be sure to sip consistently (e.g. every ~15-20 minutes) instead of chugging a lot of fluid at once.
Post-training - Replace fluid losses through normal drinking practices. If you are significantly dehydrated or need to rapidly rehydrate for your next event/training activity, try to drink ~20-24 ounces of fluid per pound of body weight lost (1,4).
Electrolytes
So far, we’ve just covered fluid needs, but what about electrolytes? Electrolytes are minerals that support a number of bodily functions like fluid balance, muscle contraction, energy production, and nerve cell communication. Common electrolytes include sodium, potassium, calcium, magnesium, and chloride, and they are found in many foods. Sodium is the most abundant electrolyte lost in our sweat, making it the primary electrolyte of concern for athletes.
Below are some common food/beverage sources of the electrolytes mentioned above:
Sodium - table salt, salted nuts or salted nut butter, pretzels, crackers, soups, cottage cheese
Potassium - bananas, potatoes, tomatoes, citrus fruits, dark leafy greens
Calcium - yogurt, milk, cheese, kale, bok choy, tofu, almonds, chia seeds, fortified non-dairy milks and fortified juices
Magnesium - green leafy vegetables, legumes, pumpkin seeds, beans, soy foods
Chloride - table salt, seaweed, shrimp, tomatoes, olives, celery (note: chloride is often naturally consumed alongside sodium and does not typically require separate planning or attention)
Electrolyte supplements have become increasingly popular in the past few years. Some savvy marketing has convinced many people that they need to use an electrolyte supplement daily in order to properly retain fluid. This is largely untrue, and certainly is not appropriate advice for the general population, who likely already consumes adequate sodium from dietary sources. However, there are certain circumstances where athletes benefit from replacing electrolytes, such as during prolonged activities or during activities completed in hot and humid weather, to name a few. Electrolyte supplementation should be planned in tandem with the fluid replacement strategy, since they have a tight relationship in the body (5).
Overhydration
If you’ve read this far, you might be tempted to go all in on dehydration prevention. Not so fast! Water can be harmful if consumed in excess. Overhydration involves drinking far beyond urine/sweat losses. It can lead to nausea, vomiting, headaches, and other unpleasant symptoms. One of the most concerning potential consequences of overhydration is hyponatremia, or low blood sodium concentration. If not treated promptly and properly, hyponatremia can result in seizures, coma, and death. For this reason, it’s important to develop a hydration plan that considers your specific needs, as “more” is not always better. To avoid overhydration, pay attention to your body's signals rather than forcing fluids. If you're urinating frequently and your urine is completely clear (not just pale yellow), you may be drinking more than necessary.
Putting It All Together
There’s no universal hydration formula that works for every athlete and your optimal approach will depend on your body, your sport, weather conditions, and several other factors. For example, an endurance athlete may need a more structured hydration plan than an athlete participating in shorter, high-intensity or team-based sports.
The best thing that you can do to improve your hydration is experiment with different fluid and electrolyte replacement strategies during training and find what feels best for you. Start with some of the baseline recommendations in this post and adjust as needed based on trial and error. Once you’ve figured out a good strategy for you, make sure to test it out in different environmental conditions/weather if you can.
If you’re struggling to make sense of the guidelines above and want help building a personalized hydration plan that supports your health and performance, reach out to me or book an appointment for individualized guidance.
References
Thomas DT, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: nutrition and athletic performance. Med Sci Sports Exerc. 2016;48(3):543-568. doi:10.1249/MSS.0000000000000852
Kerksick CM, Wilborn CD, Roberts MD, et al. ISSN exercise & sports nutrition review update: research & recommendations. J Int Soc Sports Nutr. 2018;15(1):38. doi:10.1186/s12970-018-0242-y
Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. National Academies Press; 2005. https://www.nap.edu/catalog/10925/dietary-reference-intakes-for-water-potassium-sodium-chloride-and-sulfate
Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377-390. doi:10.1249/mss.0b013e31802ca597
McCubbin AJ. Sodium intake for athletes before, during and after exercise: review and recommendations. Perform Nutr. 2025;1(1):11. doi:10.1186/s44410-025-00011-9.