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How Much Water Should You Drink?

Written by Teo Buzas, PT, DPT


The human body is mostly made up of water and is essential for life. Without water, humans can only survive for a few days. The adult human body averages about 60% water, and the brain is composed of about 73% water (1). Even mild levels of dehydration can produce disruptions in mood and cognitive functioning (2). Not drinking enough water can reduce oxygen to the brain and cause your brain to physically shrink! During athletic activity, it is common for athletes to lose 6–10% of body weight in sweat loss, causing dehydration if fluids are not replenished (2).

When being physically active, even under mild levels of dehydration will lead to a decrease in performance because of reduced endurance, increased fatigue, and increased effort (3, 4). Rehydration can reverse these deficits!

While we are being active, drinking just to quench our thirst may not be enough to offset dehydration. Dehydration can persist after you’re done with your physical activity. Hydration is especially important in hot climates. Performance in hot climates is affected to a greater degree than performance in cold temperatures (5, 6).

So how are you hydrating with your physical activity? What about in the gym and on the golf course or tennis court? When we are staying active, we may not hydrate enough when drinking according to thirst. Therefore, we need to be mindful and plan to stay hydrated. Don’t let water be what is holding you back because you cannot afford to react slower, lose focus and clarity.

Because of the complexity of bio-individuality and the many factors influencing requirements, there is no set daily amount of fluid recommend for all people to drink.

A common recommendation for a starting point an amount of daily water intake is:

Half of your body weight, in ounces.


Here is also a refence for recommended water intake by the American Health Organization (7):

Age Recommended fluid intake (milliliters per day)
0–6 months 700
6–12 months 800
1–2 years 1,300
4–8 years 1,700
9–13 years (males) 2,400
9–13 years (females) 2,100
14–18 years (males) 3,300
14–18 years (females) 2,300
Adult male 3,700
Adult female 2,700
During pregnancy 3,000
While breastfeeding 3,800


At Bridging the Gap Physical Therapy, we are here for you. We offer full body evaluations and discuss your treatment plan. This includes your diagnosis, your goals, and the plan for getting you there. Find out more by speaking to our team today at 239-676-0546.



  1. Mitchell H.H., Hamilton T.S., Steggerda F.R, and Bean H.W. The chemical composition of the adult human body and its bearing on the biochemistry of growth.
  2. Popkin B.M., D’Anci K.E. and Rosenberg I.H. Water, Hydration and Health. Nutrition Reviwes. 2010 Aug; 68(8): 439–458.
  3. Cheuvront SN, Carter R, 3rd, Sawka MN. Fluid balance and endurance exercise performance. Curr Sports Med Rep. 2003;2:202–208.
  4. Montain SJ, Coyle EF. Influence of graded dehydration on hyperthermia and cardiovascular driftduring exercise. J Appl Physiol. 1992; 73:1340–1350.
  5. Cheuvront SN, Carter R, 3rd, Castellani JW, Sawka MN. Hypohydration impairs endurance exercise performance in temperate but not cold air. J Appl Physiol. 2005;99:1972–1976
  6. Kenefick RW, Mahood NV, Hazzard MP, Quinn TJ, Castellani JW. Hypohydration effects on thermoregulation during moderate exercise in the cold. Eur J Appl Physiol. 2004;92:565–570.
  7. Armstrong L.E. and Johnson E.V. Water intake, water balance, and the elusive daily water requirement. Nutrients. 2018 Dec; 10(12): 1928.