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At Healthfully, we strive to deliver objective content that is accurate and up-to-date. Our team periodically reviews articles in order to ensure content quality. The sources cited below consist of evidence from peer-reviewed journals, prominent medical organizations, academic associations, and government data.
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How to Determine How Much Water to Drink
Guidelines define how much water an individual needs to be healthy, though some people lead lifestyles or have conditions that require more water than usual; therefore, these guidelines may not apply to everyone. For most people, however, the body is a well-oiled machine that will let you know when you need more water, and it's not necessary to overanalyze how much water to drink.
Know the general guidelines for you as an individual. The Institute of Medicine lays out the approximate amount of water traditionally thought necessary for males and females of varying age groups and lifestyles in liters per day. The IOM recommends males 19 to over 70 years of age consume 3.7 liters of water daily. Women in the same age group only require 2.7 liters. Adolescents and young children typically require less water. Pregnant women were told to consume 3 liters of water a day, while lactating women were said to require the most water of all at 3.8 liters daily. On the other hand, a 2011 study in the "British Medical Journal" noted that the recommendation to drink the equivalent of six to eight glasses a day has not been confirmed by studies 2. The author said that the recommendation is excessive, and that thirst is the best indicator of need.
How Many Milliliters of Water Should You Drink a Day?
Drink more water than usual if you are working out, hiking, or spending time at higher altitudes or in hot temperatures, as these activities can more easily lead to dehydration. You should also drink more water, and fluids in general, when you're sick, because vomiting, diarrhea and fever cause you to lose more water than you do when you are in good health.
Drink water whenever you experience thirst or a dry mouth because these are usually signs that your body is already dehydrated. Lack of saliva, inability to produce tears and infrequent urination are other signs you should likely be drinking more water. Fatigue, lethargy, muscle weakness, dizziness and an inability to focus can also be signs of dehydration. If your urine is not clear, you're not getting enough water.
Not all the water you consume will come from a glass of water itself. According to the HSPH, approximately 80 percent of a person's water intake comes from beverages, while the rest comes from food.
Though rare, it is possible to drink too much water, and the results of water intoxication can be life-threatening. Certain medical conditions may also require a specified fluid intake, in which case you should consult a health professional about how much water to drink.
How Many Milliliters of Water Should You Drink a Day?
How Many Liters of Water Should You Drink?
What Are the Effects of Water Intake on the Human Body?
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- Harvard School of Public Health: Healthy Beverage Guidelines
- British Medical Journal: Waterlogged?
- Boschmann M, Steiniger J, Hille U, et al. Water-induced thermogenesis. J Clin Endocrinol Metab. 2003;88(12):6015-19. doi:10.1210/jc.2003-030780
- M&Ms. Nutritional facts for personalized M&M'S chocolate candies. 2020.
- Brown CM, Dulloo AG, Montani JP. Water-induced thermogenesis reconsidered: the effects of osmolality and water temperature on energy expenditure after drinking. J Clin Endocrinol Metab. 2006;91(9):3598-3602. doi:10.1210/jc.2006-0407
- American College of Sports Medicine. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377-90. doi:10.1249/mss.0b013e31802ca597
- Dietary reference intakes: electrolytes and water. In: Otten JJ, Hellwig JP, Meyers LD, eds. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, D.C.: National Academies Press; 2006.
- Stookey J. Negative, null and beneficial effects of drinking water on energy intake, energy expenditure, fat oxidation and weight change in randomized trials: a qualitative review. Nutrients. 2016;8(1):19. doi:10.3390/nu8010019
- Garibotto G, Sofia A, Saffioti S, Bonanni A, Mannucci I, Verzola D. Amino acid and protein metabolism in the human kidney and in patients with chronic kidney disease. Clin Nutr. 2010;29(4):424-33. doi:10.1016/j.clnu.2010.02.005
- Dubnov-Raz G, Constantini NW, Yariv H, Nice S, Shapira N. Influence of water drinking on resting energy expenditure in overweight children. Int J Obes. 2011;35(10):1295-1300. doi:10.1038/ijo.2011.130
- Arnaoutis G, Anastasiou CA, Suh H, et al. Exercise-associated hyponatremia during the Olympus Marathon Ultra-Endurance Trail Run. Nutrients. 2020;12(4):997. doi:10.3390/nu12040997
- American Academy of Family Physicians. Hydration for athletes. Updated August 13, 2020.
- Not all the water you consume will come from a glass of water itself. According to the HSPH, approximately 80 percent of a person's water intake comes from beverages, while the rest comes from food.
- Though rare, it is possible to drink too much water, and the results of water intoxication can be life-threatening. Certain medical conditions may also require a specified fluid intake, in which case you should consult a health professional about how much water to drink.
Alissa Fleck is a contributing writer for several community newspapers in New York City. She writes book reviews for an online magazine and hosts a monthly reading series. Fleck has also interned at a literary agency and worked as a university teaching assistant. She holds a B.A. in English and an M.F.A. in creative writing.