drinking waterDiet & Nutrition

How Much Water Should You Drink a Day? (Water FAQ’s)

So how much water DO you need to drink a day? Is “8 glasses a day” really true? What if you just don’t like water? And does coffee count? Today, I will address the most commonly asked questions about fluid intake and give you essential tips on how much to drink, what to choose, and when.

How Much Water Should You Drink Daily?

How much water you should drink on a daily basis depends on several factors–activity level, body mass, the kind of climate you live in, your overall health–the Institute of Medicine has determined that the adequate daily fluid intake for an average person* living in a temperate climate is:

2.2 liters  =  75 oz  =  9 glasses

3 liters  =  100 oz  =  12.5 glasses

But what about for you? If you want to be more precise, you can simply halve your weight (in pounds) to find the number of ounces of water you should be aiming for each day:

Your weight (lbs) ÷ 2 = Daily goal (oz)

Frequently Asked Questions about Water

What counts as “fluids?”

How Much Water Should You Drink a Day coffee

  • In short: Everything besides alcohol. Milk and sports drinks are the best alternatives. Juices and broths are also okay, but be mindful of the calorie/sodium content.
  • Caffeinated beverages: When it comes to determining how much water to drink, people often wonder if  beverages such as sodas, tea, and coffee “count” toward this daily quota. The answer is technically YES. This was initially debated given that caffeine can act as a mild diuretic, but recent studies show that this effect is negligible for most people who drink moderate amounts of caffeine and that it does not offset its hydrating properties. With that said, I personally still try to drink water and coffee in a 1:1 ratio (as it makes me feel more hydrated), and recommend choosing water or lightly flavored water as the healthiest choice for meeting your daily goal.
  • Alcohol: Alcohol does not count as part of the water quota, and taken alone, it will actually dehydrate you. Always try to drink water in a 1:1 ratio to any alcoholic beverage.

Are you dehydrated? How to tell and how to prevent it:

how much water should you drink a day dehydration

  • Check your urine. When it comes to determining how much water to drink, a simple way to gauge your hydration status is to look at the color of your urine. It should appear nearly clear to light yellow. Darker than that? You are dehydrated and need to start drinking more.
  • Watch for these symptoms: Sometimes the first symptom of dehydration is just fatigue, a headache, or the feeling of not being quite right. So for example, if you are a busy professional who finds him or herself getting frequent headaches and a mid-day slump, it could be dehydration. Try increasing your water intake.
  • Get in the habit of drinking a glass at set times each day: I recommend drinking a glass of water in the morning and before each meal. This is not only a good way to ensure you stay hydrated throughout the day but will also help prevent overeating.
  • And sip throughout the day: Do not wait until you are thirsty to drink. By then your body is already edging toward dehydration. Invest in a nice reusable water bottle and keep it with you during the day.

When should you increase your fluid intake?

How much water you should drink also depends on your overall health status. Here are some circumstances where it would be a good idea to make sure your body is even more hydrated:

  • Whenever you are sick: Changes in metabolic demand during illness increase your body’s fluid requirements. In addition, fever, vomiting, and diarrhea can all quickly dehydrate you. In these cases, sports drinks or oral rehydration solutions such as Ceralyte can offer further benefit by replenishing your electrolytes (see below).
  • Whenever you are at high altitudes: At elevations greater than 8,200 feet (2,500 meters), your physiology changes and your body requires more fluids to function properly. It is recommended that you try to double your fluid intake whenever traveling to these areas.
  • If you are pregnant or breastfeeding: The Institute of Medicine recommends increasing fluid intake to 10 glasses (2.3 liters) when pregnant and 13 glasses (3.1 liters) of fluids when breast-feeding.
  • Whenever you sweat or increase your physical activity in general.

When should you drink electrolyte-containing drinks (eg. Gatorade)?

how much water should you drink a day drinks

  • In short:
    • Whenever you find yourself sweating profusely (for any reason) for more than 1½ hours.
    • Whenever you are sick and are having episodes of vomiting or diarrhea.
  • This is mainly to replace the sodium, potassium, and chloride lost through sweat and body fluids, while adding some nutrients in the form of carbohydrates. So for instance, if you exercise in a cool, dry environment for 2 hours and barely sweat, you would be just fine drinking plain water.

Do you need to worry about drinking too much water?

  • In short: For the average, healthy person: NO
  • In order for a healthy person to get hyponatremia (the serious condition that occurs when you drink so much water that it overwhelms your kidneys and dilutes your body’s sodium), it is estimated that an average person would need to drink approximately 6 liters of water over a very short period of time (such as in a water-drinking contest or in attempt to rehydrate after a marathon).
  • Those at risk (eg. athletes), should always drink fluids supplemented with electrolytes when drinking large amounts (eg. after a game).
  • If you have congestive heart failure, kidney disease, or certain other conditions, you may actually need to watch your water intake and drink in moderation. In all cases, do what your personal physician has advised you to do.

So with that said, be encouraged to go forth and drink to better health!

*You can find more essential health information like this in Being Empowered for a Healthy Heart: A personal guide to taking control of your health while living with chronic conditions, by Phoebe Chi, MD, MPH.

Phoebe Chi, MD
Phoebe Chi, MD

As a physician, clinical educator, and managing editor of PhoebeMD: Medicine + Poetry, Dr. Chi aims to inspire, educate, and empower the reader community. She is the author of Being Empowered for a Healthy Heart: A personal guide to taking control of your health while living with chronic conditions, a poetry-infused health guide, and founder of Pendants for a Cause, a nonprofit organization aimed toward helping others.

68 replies »

  1. Great post! A lot of people don’t even close to drinking enough water, and this is a helpful guide. I didn’t drink much water until I got kidney stones in college—I learned my lesson! Now I put a little lemon or lime in my water and it’s a lot easier to get that daily intake. Thanks for the information!

  2. I just downloaded an app on my phone that dings every hour for about 8 hours, to remind me to drink water. I have to be reminded or my coffee consumption will be through the roof! Great and helpful article…Thank you! <3

  3. Thanks for the excellent article, Phoebe! As a typical teen in the 60s involvedin youth and scholastic sports, we were beset with the notion of “water discipline” and it is a wonder the vast majority survived such teachers and coaches. Later in Marine Corps “boot camp” the term “Water Discipline” was spelled in ALL CAPS, and again the wonder mostly was repeated. As a combat correspondent in Vietnam I carried 10 1-quart canteens, two 3-quart “blivets” and often a six-pack of beer hidden in the bottom of a pack-frame rucksack that weighed – after 10 months counting camera and writing gear, food and protection: rifle, ammo, flak jacket, etc. – almost and often a little more than I. When possible, especially in the beautiful but dangerous mountains with plenty of fast-flowing streams, I’d cycle through the water-load (8.8 pounds per gallon and up to well-past 10 salt tablets a day) two and if possible three times a day. My camouflaged utility jacket was white with extruded salt and I sweated rivers, but never had a cramp or any heat-borne debilitation. When much later I was reading about crossing deserts and other water-short lands, the author asked how would you carry one gallon of water across 20 miles of dessert? Instantly I though: in my belly! Leave both hands free; protect the fluid from getting too hot; and use the perspiration engendered as a cooling device, rather than chance external evaporation – when I spoke to the writer much later I recalled his question – and my answer – and he grinned: “wasted our time, me writing and you reading,” and I replied, grinning equally large: “no knowledge already obtained and later reinforced ever is wasted.” Again, Thanks, Puppydoc!

  4. Hi Phoeb’s. I understand for every coffee we drink we should drink 2 glasses of water to help flush our kidneys and liver. Luckily I don’t have an 8 cups a day coffee habit. Ideas for how I deal with the how many times I have to pee problem? Cheers,H

    • Hi Helen. 🙂 Yes, that used to be the thought–mainly the “flushing out” is to address the mild “dehydrating effects” of caffeine, as dehydration firstly affects the kidneys. However, what studies have found more recently is that 1) for people who are already tolerant to caffeine, this effect is negligible…and 2) it takes a fairly large dose of caffeine to create a significant diuretic effect (500mg).

      Personally, I like to drink coffee and water in a 1:1 ratio because it makes me feel more hydrated, but technically, one doesn’t even have to do that. If you are talking about “flushing out” your organs in a different way (such as in a ‘detox’ way) and it motivates you to drink more, then by all means…continue with the habit. I always say that anything that gets you to drink more water is a good thing.

      Also, remember everyone is different, so always take the advice of your own physician over any other source.

      Hugs! 🙂

  5. Let’s just say I am very disappointed that wine is not on the “good” side of things in this post….:) Thanks for the info Doc…. as always you are appreciated in your efforts… 🙂

  6. Very useful information. I knew someone that did not drink much water in the winter, stating, it is cold out (or something to that affect). I look forward to more useful information.

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