How Much Water Do You Really Need to Drink a Day?

If you’ve ever felt light-headed and glanced at your neglected water bottle, you might have realized pretty quickly that you never actually use it when you’re not in the gym. Or maybe you staunchly believe that your three cups of morning coffee count as hydration. (Spoiler: research says it does. Kind of. It’s complicated).

Whether you’re predisposed to always sipping that sweet H2O or your mouth is constantly a desert, you’ve probably heard the eight glasses per day recommendation that everyone and their mother seems to give. But figuring out how much water you really need to drink every day may be more complicated than that. This is especially true when you’re trying to figure out if hydration impacts your gains in the gym? (Another spoiler: it sure does.)

If you’re doing everything you can within your training program to maximize your strength and muscle growth but aren’t getting enough water, you might be missing out on a lot of progress. Unless you’re at risk of dehydration, you can likely benefit from listening to your body and drinking when you feel like it — while keeping in mind the daily water recommendations in your region. It can benefit your training (and daily life) to know how much water is enough and whether you can actually drink too much water. The more you know, the more you can step it up on the platform.

How Does Hydration Impact Your Workouts?

Hydration is crucial for maintaining and even improving your lifting prowess. You’re more likely to perform better on the platform when you have enough water in your system. Drinking enough water both before and during your workout can help your heart rate recover faster and improve overall exercise performance. (1)

On the flip side, working out while dehydrated can negatively impact an athlete’s performance and even increase injury risk. (2) What constitutes dehydration varies from person to person. Depending on how much an athlete sweats, the environment they’re working out in, and their own body’s tolerance to dehydration, recommendations vary for how much water they need. (3) That said, staying well-hydrated — drinking between two and two and a half eight-ounce cups of water — during the two or three hours before training may stave off those negative effects. (2)

[Read More: The Best Home Gym Equipment, Tested and Verified by Experts]

How Much Water Do You Actually Need Each Day?

While many people are familiar with the nebulous eight glasses of water per day recommendation, different organizations have different standards for what they recommend for your fluid intake. For example, the Institute of Medicine’s Water Intake Recommendations suggest between 11 and 16 cups of water (eight ounces per cup) each day. (11)

Recommendations from the European Food Safety Authority vary from about eight and a half to 11 cups per day, while the US’s National Academy of Medicine recommends between nine and 13 cups a day. (4) These recommendations also often assume that people have access to safe drinking water, a lack of which has been shown to have severely negative physical and mental health outcomes. (12)

Factors That Impact Water Recommendations

Daily water intake recommendations are complicated because they are influenced by so many factors. Knowing what goes into daily water intake recommendations can help you make informed decisions about your own drinking habit.

Your Personal Lifestyle and Body Needs

How much water you need is shaped by everything from what you eat to whether you have an active or generally sedentary lifestyle. (4) Your kidneys, sweat glands, and perceptions of thirst all impact your water intake, especially when you’re engaging in continuous or intermittent physical work over long periods of time (between five and 18 hours). (13)

Cultural Behaviors and Expectations

How much water you need to drink seems to be influenced by cultural expectations and food and beverage consumption. 

For example, cultural expectations about women and men’s activity levels and eating habits may impact the gendered differences in hydration needs in industrialized countries. (14)

How Much You Exercise

Exercising also impacts how much you sweat day-to-day. Even when they’re not currently exercising, people who work out regularly with high intensity tend to sweat more in everyday life. (15) Additionally, people who are pregnant or lactating have unique hydration needs that are greater than their non-pregnant peers. (16)

How Much Tea and Coffee You Drink

Where you’re getting your water makes a difference, too. How much juice, sugary drinks, coffee, or tea that people drink influences how much of their hydration comes from plain water. (17) And yes, the idea that “coffee is mostly water” seems to be pretty true — research suggests that your morning energy-booster doesn’t necessarily dehydrate you, and helps contribute to your fluid intake. (18)

So How Much Water Should You Drink?

Since there’s so much variability within standardized guidelines, how should you interact with water intake recommendations? If you’re in a situation where you’re likely to get dehydrated — say, you’re sweating a lot, in a very hot environment, or have a medical condition that requires you to pay particular attention to your hydration — research suggests that following recommended water guidelines is very helpful. (19)

However, if you’re not at risk of becoming dehydrated, you’re likely alright if you simply drink when you feel thirsty. (19)(20) Paying close attention to your own body — for example, how much you’re sweating throughout a workout or during your day — can help you stay better hydrated than just drinking what you think you should be drinking. (1) 

[Read More: Best Meal Replacement Shakes, With Dietitian Advice]

Benefits of Staying Hydrated

You may not love running to the bathroom for a bio break after downing your daily recommended glasses of water, but that doesn’t mean it’s not worth it. There are plenty of reasons to stay hydrated, both in and out of the gym.

Help Prevent Diseases

Leaving your water bottle relatively untouched for a day or two probably won’t hurt you in the long run. But chronically low water intake is related to disease and metabolic dysfunction. (4) By increasing water intake to at least 1.3 to two liters a day, research suggests people have the potential to lower their blood pressure, dilute waste materials in their blood, protect their kidney function, and increase their body temperature. (5)

Improve Your Mental Health

If you’ve ever been grumpy and someone’s told you to HALT (check if you’re hungry, angry, lonely, or tired), they’re doing a great job at covering your bases. But you might want to add an extra T to that check-in — thirsty.

It turns out that not drinking enough water can negatively impact your mental health. You’re more likely to be anxious and tense when you’re even a little bit dehydrated (which might be why your friend is telling you to HALT). (6)

Staying well-hydrated helps you feel more awake during the day and also boosts your mood, sense of calmness, and life satisfaction. On the other hand, being dehydrated has negative impacts on these same life factors. (7) Staying hydrated with plain water is also associated with reduced symptoms of depression, and to a lesser extent, lessened anxiety. (8)

Boost Cognitive Function

It’s not a coincidence that you probably feel more clear-headed after you hydrate. Drinking enough water has been shown to increase your attentiveness to your visual surroundings and short-term memory. (9)

When you’re not drinking enough, you’re likely to be less vigilant, process information slower, and have more difficulty with your memory. (6)(10) So sipping water during those work calls might actually help you get those spreadsheets done faster and better.

Enhance Workout Performance

Trying to work out when your body needs water can be an exercise in physical discomfort and futility. Working out without adequate hydration can hinder your performance in the gym and increase your risk of injury. (2) But working out while well-hydrated can improve your performance generally while also helping in specific ways, like bringing your heart rate back to normal more efficiently during and after bouts of exercise. (1)

How to Tell if You’re Dehydrated

If you’re thirsty or your lips are pretty dry, you probably know to grab yourself some H2O (and perhaps some chapstick). But you don’t have to reach dangerous levels of dehydration to be able to recognize some symptoms of not having enough water in your system.

Lack of focus, lightheadedness, headaches, muscle cramps or weakness, rapid breathing, and fatigue are all signs that you could be dehydrated. (21) Studies also suggest that darker yellow urine can also serve as a reliable indicator of dehydration (as opposed to relatively clearer urine). (22)(23)

How Much Water is Too Much Water?

Maybe you drink well over the classically recommended 64 ounces of water per day, just to cover your bases. That might be fine for your body, but more doesn’t always mean better. Drinking more than the recommended eight glasses of water per day doesn’t necessarily improve on the benefits of staying hydrated, except perhaps in preventing recurring kidney stones. (24)

If you’re not sweating and you’re not feeling particularly thirsty — even during a workout — fluid replacement might not be super necessary. You can get too hydrated when you take in more water than you put out, which can increase your stress levels and negatively impact the quality of your training. (25)(26)

So, pay attention to how much you’re sweating, how much sodium you’re taking in, and how often you’re using the restroom when determining how much water you need to take in. You don’t have to drink water just to drink it, especially if it’s making your body less comfortable.

How to Hydrate for Your Workout

Beyond following the gist of most recommendations (which generally range from eight to 16 cups of water a day), how you hydrate while exercising is largely up to you. Context is important when you’re figuring out how to stay hydrated during your training session. If you’re working out in the heat, you’ll likely want to drink a lot more than if you’re in pretty non-sweaty conditionings.

You also have to take into account how hydrated you’ve been throughout the day by the time you hit the gym. In the two to three hours immediately prior to your workout, try to drink between two and two and a half cups of water to prepare your body for the effort. (2)

If you haven’t hydrated well in the hours prior or are working out in a hot environment, you’ll need to step up your hydration game during training. Try sipping water a little as needed while working out, based on your understanding of your sweat and thirst levels. (19) 

When you tend to sweat a lot during your workout, you’ll likely need to sip more water than your gym buddy who doesn’t seem to have any sweat glands. (1)(27)(3) Studies suggest that you’re more likely to stay hydrated if you have ready access to water during your workout, so keep your bottle next to the squat rack. (2)

Drink Up

If you’re the type to constantly have a water bottle in hand, have at it — just make sure your body feels good when you drink rather than like you’re weighing yourself down. And if coffee is your primary mode of hydration, well, research says you might not be in too much trouble — as long as you’re also getting water from actual water.

References

1. Ayotte, D., Jr, & Corcoran, M. P. (2018). Individualized hydration plans improve performance outcomes for collegiate athletes engaging in in-season training. Journal of the International Society of Sports Nutrition, 15(1), 27.
2. Judge, L. W., Bellar, D. M., Popp, J. K., Craig, B. W., Schoeff, M. A., Hoover, D. L., Fox, B., Kistler, B. M., & Al-Nawaiseh, A. M. (2021). Hydration to Maximize Performance and Recovery: Knowledge, Attitudes, and Behaviors Among Collegiate Track and Field Throwers. Journal of human kinetics, 79, 111–122.
3. Casa, D. J., Armstrong, L. E., Hillman, S. K., Montain, S. J., Reiff, R. V., Rich, B. S., Roberts, W. O., & Stone, J. A. (2000). National athletic trainers’ association position statement: fluid replacement for athletes. Journal of athletic training, 35(2), 212–224.
4. Armstrong, L. E., & Johnson, E. C. (2018). Water Intake, Water Balance, and the Elusive Daily Water Requirement. Nutrients, 10(12), 1928.
5. Nakamura Y, Watanabe H, Tanaka A, Yasui M, Nishihira J, Murayama N. Effect of Increased Daily Water Intake and Hydration on Health in Japanese Adults. Nutrients. 2020 Apr 23;12(4):1191.
6. Ganio MS, Armstrong LE, Casa DJ, McDermott BP, Lee EC, Yamamoto LM, Marzano S, Lopez RM, Jimenez L, Le Bellego L, Chevillotte E, Lieberman HR. Mild dehydration impairs cognitive performance and mood of men. Br J Nutr. 2011 Nov;106(10):1535-43.
7. Pross, N., Demazières, A., Girard, N., Barnouin, R., Metzger, D., Klein, A., Perrier, E., & Guelinckx, I. (2014). Effects of changes in water intake on mood of high and low drinkers. PloS one, 9(4), e94754.
8. Haghighatdoost, F., Feizi, A., Esmaillzadeh, A., Rashidi-Pourfard, N., Keshteli, A. H., Roohafza, H., & Adibi, P. (2018). Drinking plain water is associated with decreased risk of depression and anxiety in adults: Results from a large cross-sectional study. World journal of psychiatry, 8(3), 88–96.
9. Benefer MD, Corfe BM, Russell JM, Short R, Barker ME. Water intake and post-exercise cognitive performance: an observational study of long-distance walkers and runners. Eur J Nutr. 2013 Mar;52(2):617-24.
10. Ritz P, Berrut G. The importance of good hydration for day-to-day health. Nutr Rev. 2005 Jun;63(6 Pt 2):S6-13.
11. Riebl, S. K., & Davy, B. M. (2013). The Hydration Equation: Update on Water Balance and Cognitive Performance. ACSM’s health & fitness journal, 17(6), 21–28.
12. Slekiene J, Mosler HJ. The link between mental health and safe drinking water behaviors in a vulnerable population in rural Malawi. BMC Psychol. 2019 Jul 8;7(1):44.
13. Armstrong LE. Assessing hydration status: the elusive gold standard. J Am Coll Nutr. 2007 Oct;26(5 Suppl):575S-584S.
14. Manz F, Wentz A. 24-h hydration status: parameters, epidemiology and recommendations. Eur J Clin Nutr. 2003 Dec;57 Suppl 2:S10-8.
15. Leiper JB, Pitsiladis Y, Maughan RJ. Comparison of water turnover rates in men undertaking prolonged cycling exercise and sedentary men. Int J Sports Med. 2001 Apr;22(3):181-5.
16. McKenzie, A. L., Perrier, E. T., Guelinckx, I., Kavouras, S. A., Aerni, G., Lee, E. C., Volek, J. S., Maresh, C. M., & Armstrong, L. E. (2017). Relationships between hydration biomarkers and total fluid intake in pregnant and lactating women. European journal of nutrition, 56(6), 2161–2170.
17. Guelinckx, I., Ferreira-Pêgo, C., Moreno, L. A., Kavouras, S. A., Gandy, J., Martinez, H., Bardosono, S., Abdollahi, M., Nasseri, E., Jarosz, A., Ma, G., Carmuega, E., Babio, N., & Salas-Salvadó, J. (2015). Intake of water and different beverages in adults across 13 countries. European journal of nutrition, 54 Suppl 2(Suppl 2), 45–55.
18. Killer SC, Blannin AK, Jeukendrup AE. No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population. PLoS One. 2014 Jan 9;9(1):e84154.
19. Backes, T. P., & Fitzgerald, K. (2016). Fluid consumption, exercise, and cognitive performance. Biology of sport, 33(3), 291–296.
20. Armstrong LE. Rehydration during Endurance Exercise: Challenges, Research, Options, Methods. Nutrients. 2021 Mar 9;13(3):887.
21. Shaheen, N. A., Alqahtani, A. A., Assiri, H., Alkhodair, R., & Hussein, M. A. (2018). Public knowledge of dehydration and fluid intake practices: variation by participants’ characteristics. BMC public health, 18(1), 1346.
22. Zhang N, Du S, Zheng M, Tang Z, Yan R, Zhu Y, Ma G. Urine color for assessment of dehydration among college men students in Hebei, China – a cross-sectional study. Asia Pac J Clin Nutr. 2017;26(5):788-793.
23. Kostelnik SB, Davy KP, Hedrick VE, Thomas DT, Davy BM. The Validity of Urine Color as a Hydration Biomarker within the General Adult Population and Athletes: A Systematic Review. J Am Coll Nutr. 2021 Feb;40(2):172-179.
24. Meinders AJ, Meinders AE. Hoeveel water moeten we eigenlijk drinken? [How much water do we really need to drink?]. Ned Tijdschr Geneeskd. 2010;154:A1757.
25. Maughan RJ, Meyer NL. Hydration during intense exercise training. Nestle Nutr Inst Workshop Ser. 2013;76:25-37.
26. Judelson DA, Maresh CM, Farrell MJ, Yamamoto LM, Armstrong LE, Kraemer WJ, Volek JS, Spiering BA, Casa DJ, Anderson JM. Effect of hydration state on strength, power, and resistance exercise performance. Med Sci Sports Exerc. 2007 Oct;39(10):1817-24.
27. Maughan RJ, Shirreffs SM. Dehydration and rehydration in competitive sport. Scand J Med Sci Sports. 2010 Oct;20 Suppl 3:40-7.

Featured Image: LightField Studios / Shutterstock