How Much Water Should I Really Be Drinking?

Maybe fish have had it right all along.

In fact, “You’re probably dehydrated,” is the boring answer to a frightening number of our everyday questions. Why am I still hungry if I just ate? Why is my skin dry if I’m moisturizing? Why do I feel unwell after drinking nine glasses of wine last night?

But with all the contradictory advice floating around, hydration can feel like a game with ever-changing rules. And that’s not entirely unfair, because, according to Dr. Hanson Lenyoun, the rules vary by individual. Dr. Lenyoun is a former surgeon and one of the geniuses behind Pryme Vessyl, a drinking glass that serves as a personalized hydration metric, and he spoke to us about how much water we should really be drinking.

So, how much water should I be drinking every day?

It’s not about drinking 8 glasses of water each day. Our hydration needs are dynamic and unique to each one of us. They’re influenced by our age, weight, height and they change constantly based on how active (or not) we are and how much sleep we get (or don’t). Think about Laila Ali (professional boxer) versus Miley Cyrus: very different women who do very different things. Why would we tell them to drink the same amount of water?

Is there a specific equation to figure out how much I should drink?

The Institute of Medicine recommends that adult women consume 2.7 L (91 oz) of total water per day, and adult men consume 3.7 L (125 oz).

However, this is total water, so those numbers include that which you consume in the food you eat. Since the average American consumes around 20% of their water needs through food, that leaves 2.2 L (74 oz = 9 cups) for women and 3 L (101 oz = 13 cups) for men.

But, like I said, an individual’s needs can vary drastically depending on a variety of factors. Many hydration calculators exist online that take unique characteristics like your biological sex, height, weight, and age into account to help you understand where you fall in the spectrum.

They’re often missing a few key factors like activity level and your environment’s climate, which we built into Pryme Vessyl.

What are the three most important reasons I should strive to hit my personal daily target?

1. You want to perform at your best. Studies have shown that even mild dehydration can negatively impact your physical and mental performance. Impacts were seen on endurance, recovery time, motivation, mood, attention, memory, energy levels and even immune system function.

2. You want to look your best. Your skin contains approximately 30% water and the middle layer acts like a sponge, so optimizing your hydration helps keep it plump, elastic and resilient. Bonus: drinking water also helps with oral hygiene and can keep bad breath at bay.

3. Dehydration is the new smoking. Recent studies have shown that dehydration could affect vascular function in a way that is “similar to smoking a cigarette.” This underscores the importance of being at your Pryme (heh) – staying on top of your hydration is of utmost importance. The deleterious effects of dehydration can set in before you’re even thirsty.

What’s more important: drinking water in the morning or the evening?

Drinking water in the morning has clear benefits. The fact that you’ve been sleeping means you haven’t been drinking and you’re likely mildly dehydrated when you wake up. For this reason it’s important to hydrate early.

On the flip side, drinking too much water late at night can actually have some negative impacts. Nocturia, or needing to urinate multiple times throughout the night, can be frustrating and can negatively impact the quantity and quality of the sleep you get.

Got it. So how much water should I drink when I wake up?

More important than a specific quantity is your timeliness. Get in the habit of drinking a glass of water shortly after waking up, because your hydration needs will only grow as the day goes on. Start early so you’re optimally hydrated and performing at your best throughout the day.

Should I drink at all before sleeping?

In our crazy, connected world, sleep is a precious commodity. Over-hydrate before bed and you’ll risk disrupting it. We’ve all seen people walking around the block at 11pm trying to hit 10,000 steps before bed — this is NOT the way you should think about hydration.

You’d do better to focus on drinking consistently throughout the day when you actually need it. If you’re thirsty before bed, it’s fine to have a few sips, but I’d leave it at that.

How much water should I drink while I’m also consuming alcohol? We’ve been talking about this at Man Repeller!

Alcohol is a diuretic, which means it promotes the production of urine and can leave you dehydrated and yes: hungover. Every serving of alcohol (a shot of spirits, a glass of wine, a beer, etc) causes you to lose, on average, 4 ounces of water along with half of all the replacement fluid you consume over the following 2 hours.

A good rule of thumb to compensate for these losses is to alternate between alcoholic beverages and water. So, for each alcoholic drink you consume, follow it with a glass of water.

Is there such a thing as drinking too much water? (Once I read that a woman drowned herself from the inside out. Is this actually possible?)

Yes, there is such a thing as drinking too much water, so please don’t try it! It’s called dilutional hyponatremia, or water intoxication. This happens when there’s an imbalance between the water and salt levels in your body; too much water can cause cells to swell like water balloons. If this happens in your brain, it can be deadly.

Under normal circumstances, accidentally drinking too much water is very rare and difficult to do.

Usually the only times you’ll see this is during water-drinking contests (yep, people are actually doing this) or after long periods of intense physical activities during which excessive amounts of fluid were consumed. Previously this was only seen in extremely hot or humid areas, but more awareness around hydration is actually leading to reports across an increasingly diverse set of sporting activities including marathons, triathlons, long hikes, Bikram yoga classes, and team sports practices and games.

As such, we took this into account when developing Pryme Vessyl. The app will notify you if you are drinking at a higher rate than recommended over a period of time.

Is there a method to how I should be drinking my daily intake of water?

Absolutely. When you drink is just as important as how much you drink!

You wouldn’t drink all of your water for the entire day first thing when you wake up in the morning. We’re humans, not camels. You need to keep up with your needs as you create them (through exercise, activity, and just living).

There’s no specific formula as to how to do this, but sipping throughout the day (rather than chugging sporadically) can help keep you consistently hydrated to avoid episodes of dehydration. Research has shown us that even mild dehydration (less than 2 percent, which is around the threshold where thirst usually kicks in) can have measurable impacts on your physical and mental performance.

If I hate water but know I need to drink it, is there a way to make it more consumable? Can I eat lots of fruit or celery in place of drinking water!?

The average American consumes about 20% of their daily water needs through food, so you’re already making a dent. You can certainly up that percentage by increasing the amount of fresh fruit and vegetables in your diet.

Be careful with soups and juices though — although they have a lot of water they also have a lot of hidden “ingredients” (sodium, calories, sugar, etc). To get 100% of your needs through food would be a lot of chewing and tons of extra calories, but there are other ways you can modify your water to make it more interesting.

I like to infuse my water with fresh fruit, vegetables, and herbs. Many people also find carbonated water more palatable, but stay away from artificially flavored ones. Lastly, don’t forget about coffee and tea (they actually DON’T dehydrate you — that’s a big myth). Plain coffee and tea without other additives (cream, sugar, honey, etc.) hydrate you in the same way water does, while providing other health-promoting components like polyphenols, antioxidants, and moderate amounts of caffeine.

Dr. Lenyoun is a former surgeon and alum of Harvard and Columbia Universities. He has made it his mission to spread the word on how to get — and stay — hydrated. As Head of Health at consumer health startup Mark One, Dr. Hanson has spent the last year perfecting Pryme Vessyl, a cup that automatically tracks and displays your personal hydration needs. Using a proprietary hydration algorithm developed from years of scientific data, Pryme determines how much you should drink at each moment to stay mentally sharp and physically strong. Follow Pryme Vessyl on Instagram @vessyl.

Photographed by Krista Anna Lewis; creative direction/styling by Emily Zirimis.


Get more Beauty ?
  • Yvonne Dunlevie


    • Hanson Lenyoun

      It is, Yvonne!!! Recently, researchers at the University of Birmingham studied a group of people who regularly consume coffee and measured their fluid levels when they drank coffee compared to an equal amount of water. They found that caffeine had “absolutely no influence on hydration status” and that “coffee provides similar hydrating qualities to water.” Here’s a link to the study if you want to check it out:

      While it’s definitely not a good idea to replace all of your water consumption with coffee (too much caffeine can lead to jitters, interruptions in sleep, and other health concerns), those of us who enjoy a few cups can rejoice in the fact that we can have our coffee and stay hydrated too!

      – Dr. Hanson

      • Yvonne Dunlevie

        Wow, thanks Dr. Hanson! You’ve changed everything! Promise to continue my regular water consumption along with regular coffee!

    • Debbie

      Coffee has caffeine caffeine is diuretic

    • Brittney

      Why do I feel massively dehydrated not long after drinking coffee then? I always need to drink water within half an hour of drinking coffee, it gets to the point where my throat is actually incredibly dry if I don’t.

  • Cinamaron

    A couple years ago I started making a conscious effort to substitute water for all the soda I drank and it worked really well. Now I drink way more water and can barely stomach soda. I also now feel less bad about the amount of coffee I consume at work!

    • Yep! I stopped drinking soda years ago and now it just tastes gross to me, I don’t even like alcoholic drinks with soda (rum & coke etc). I got myself a water bottle so it’s really easy to sip throughout the day and I can measure my intake by the amount of refills I do.

  • This tumblr post has been my guiding water principle for over a year!

    • Taylor

      This is the golden (literally) rule! I’m in medical school and we were just taught by a stellar nephrologist that this is the best way to assess how much you should be drinking.

  • I drink at least 80 ounces of water during the work week. It gives me an excuse to get up and walk around. More importantly, I’m not thirsty when I go running or complete any of my races on the weekend.

  • Nae

    I used to feel weird for drinking upwards of 10 glasses of water a day on most days (I’m always thirsty), but posts like this help me realize I’m not as crazy as I seem. Well, at least when it comes to water. 🙂 Thanks for the great info!

  • Sagar

    your website is great…………

  • Alex

    Is La Croix one of those carbonated waters that you would consider to contain artificial flavorings? I’m obsessed but don’t know if they’re actually hydrating when I drink them.