You’re Probably Not Drinking Enough Water. This Is What a Registered Dietitian Recommends

Do you know how much water you drink each day? Maybe you have no idea, or maybe you’ve followed the “drink eight 8-ounce glasses a day” advice. If you follow the latter, also known as the 8 x 8 rule, you may not be getting the hydration your body needs.

“The 8 by 8 rule can be a little simplistic for some,” says Renee Fitton, a registered dietitian and director of education at L-Nutra, a nutrition technology company, adding that the rule isn’t necessarily dangerous. To help you figure out exactly how much water you should drink each day, Fitton breaks it down.

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How much water should you drink daily?

Fitton says a variety of factors affect how much water one needs daily, including body size, medications, gender, physical activity, climate, health status and altitude.

Most of us also know the old adage: drink eight 8-ounce glasses of water a day. The 8 by 8 rule advises us to drink 64 ounces (about 1.9 liters) of water per day. Many of us have blindly followed this advice all our lives, without knowing its origin or the rationale for the recommendation to drink eight glasses of water.

Apparently, the 8 x 8 rule came out of nowhere, because there is no scientific evidence to support it. It’s just another one of those long-standing myths that people believe because that’s what everyone else believes. Drinking 64 ounces of water a day isn’t bad, but it may be too much or not enough for some people.

“For some people, simple rules like these help them stay on track,” Fitton said. “If drinking eight 8-ounce glasses of water a day helps someone meet their hydration goals, then that’s a good place to start. But I wouldn’t call it the gold standard.”

Other guidelines exist but there is still no real consensus. There are no formal recommendations for how much water people should drink daily, perhaps because everyone needs different amounts of water.

There is an “adequate intake” of water for adult men and women, but it can vary from person to person. This adequate intake includes water from beverages other than water, such as milksports drinks, tea and yes, even coffee. This also includes water from fruits, vegetables, and other foods (think about how much water is in a bowl of oatmeal or soup).

Adequate intake is 15.5 cups (3.7 liters or 125 ounces) for average men and 11.5 cups (2.7 liters or 91 ounces) for average women. How you choose to consume those 125 or 91 ounces of fluid is up to you. Although this is the closest number to the recommended daily intake, even these numbers differ for each person depending on their health status.

Reasons You May Need to Drink More Water

You have an active job: Those who are on the go all day (especially those who work outdoors) may need more water than most people. The more you move, the more you sweat and you need to replace lost water (and electrolytes) with fluid intake.

If you work outdoors during a heat wave, the U.S. Centers for Disease Control and Prevention recommends drinking 8 ounces (1 cup) of water every 15 to 20 minutes while working. Drinking water before and after work can help prevent dehydration.

You exercise often: If you don’t have an active job but exercise a lot, whether at the gym or through recreational activities, you also need more water than most. Even if you don’t realize it, you lose a lot of fluid during physical activity (even in cold weather). Increase your water intake to account for activity (especially travel activities).

You live in a hot climate: Hot weather means increased sweating and it’s important to replace lost fluids. Drought worsens fluid loss in hot weather: people in desert climates may need more water than those in tropical climates.

You are pregnant or breastfeeding: Pregnant women need more water to support better circulation, increased calorie intake and other physiological processes that support their baby’s growth. Breastfeeding women need more water to support breast milk production.

Your urine is dark color: The color of your urine can tell you a lot about your hydration levels. “The color of your urine is the best and most personalized, consistent and immediate way to measure hydration throughout the day. We want to look for pee that is light yellow, not completely clear (over-hydrated) but also not dark yellow or amber (under-hydrated),” Fitton said.

You have dry mouth, chapped lips or muscle cramps: Yes, when you are dehydrated, your body lets you know. “Water is an essential substance for life, so when we lack it, our body no longer functions at its maximum capacity and this can persist in many ways and uniquely from person to person,” Fitton said.

Hydration Tips to Help You Drink More Water

Different people follow different rules when it comes to hydration. These four common guidelines can help you stay hydrated, whatever your lifestyle.

Drink when you are thirsty

There is some controversy surrounding this method. Some health professionals say you shouldn’t overcomplicate hydration and that your body tells you when it needs water. Others say that waiting until you’re thirsty is too long – that you’re already dehydrated when you’re thirsty. Some people seem to have stronger thirst mechanisms than others, so this method might not work for you.

Drink a drink before meals and between meals

That’s not bad advice. Structuring water consumption around a ritual like mealtime can ingrain hydration as a habit. Your total water intake will vary depending on the number of meals you eat. If you eat three meals, you will drink five glasses of water according to this rule, which may not be enough (unless they are large glasses). This rule probably won’t work for you if you don’t have an eating routine.

Drink eight glasses a day

Generic health advice rarely fits everyone. If you feel adequately hydrated with 64 ounces of water each day, that amount is probably enough to keep you hydrated. If you feel too hydrated (clear urine, very frequent urination, or bloating), reduce your intake slightly. If you’re feeling dehydrated (dark urine, headaches, infrequent urination, dizziness or fatigue), eight glasses may not be enough for you.

Drink half your body weight in ounces

This is a simple guideline, easy to remember and generally easy to implement. If you weigh 150 pounds, try drinking 75 ounces of water every day. This is the only rule of thumb that accounts for different body sizes, but it does not take into account thirst, climate, activity level, or other factors.

Making water visible and accessible

Fitton says keeping your water accessible at all times provides a visual reminder to drink water. She also recommends using an app like WaterMinder that sends daily reminders to drink water.

Link your water intake to your daily habits

Another great way to get your daily water intake in is to make drinking water part of your daily habits. This might look like drinking water as soon as you wake up, after eating a meal, or right before you leave the house. “These mini-habits build on things you already do, so you’re not trying to remember to do something new. The more you make hydration part of your daily routine, the easier it becomes,” Fitton said.

Experiment with hydration techniques to find what works for you. As long as you’re not struggling with chronic fatigue, dizziness, headaches, or other signs of dehydration, you’re probably doing a pretty good job. To be safe, you can always tell if you are underhydrated or overhydrated based on the color of your urine.