Do you need to drink more water every day? The answer is more nuanced than you might expect.
“There’s probably not a one-size-fits-all recommendation for how much water someone should drink, especially given the fact that we’re all shaped differently, have different kinds of exercise routines, and live in different climates,” said Benjamin Breyer, MD, chair and professor of urology at the University of California – San Francisco.
A recent review by Breyer’s team summarized 24 years of scientific studies on increased water intake. The findings suggest that drinking more water may promote weight loss (by 44% to 100%) and lower the risk of kidney stones (15 fewer events per 100 participants over five years). Staying hydrated may also help prevent migraines, improve blood sugar regulation, and reduce the likelihood of urinary tract infections and hypotension (dangerously low blood pressure). However, the researchers noted that the quality and quantity of studies on these topics are limited.
“We really do need more well-executed randomized trials in specific areas, especially where we’re seeing signals of benefit, like weight loss and kidney stones,” said Breyer.
Here’s what we currently understand about the benefits of drinking more water and how to determine whether you’re getting enough.
Benefits of Drinking More Water
The research team identified several potential health benefits of increasing water intake:
- Weight Loss: Drinking 500 milliliters (about 17 ounces) of water before each meal led to 44% to 100% more weight loss compared to control groups. A drink of this size may fill the stomach and act as a natural appetite suppressant, Breyer explained. However, simply drinking more water throughout the day without timing it before meals did not show weight loss benefits.
- Kidney Stones: Increasing water consumption lowered the risk of kidney stones and extended the time between stone occurrences by an average of 13.6 months. Higher water intake may reduce the concentration of stone-forming salts in urine.
- Blood Sugar: For people with type 2 diabetes, drinking additional water lowered fasting blood sugar levels, possibly by increasing blood volume and diluting glucose concentration. However, in individuals with normal blood sugar levels, increased water consumption led to a slight, non-harmful rise in blood sugar.
- Headaches: In one study, increasing daily water intake by 1,500 milliliters (about 51 ounces) slightly improved migraine symptoms. Another study showed no significant impact on headaches.
- Urinary Tract Infections (UTIs): Women with recurrent UTIs who initially drank less than 1,500 milliliters (about 51 ounces) of water daily experienced fewer UTIs after doubling their water intake. They also went longer between infections and required fewer antibiotics. Adequate hydration may help flush bacteria from the urinary tract.
- Overactive Bladder: Reducing fluid intake by 25% helped individuals with overactive bladder decrease the frequency and urgency of urination during the day and night.
- Hypotension: Drinking an additional 30 milliliters of fluid per kilogram of body weight (about 0.5 ounces per pound) increased arterial pressure, which may benefit people prone to very low blood pressure.
How Much Water Do You Need?
The popular guideline of eight glasses a day might not work for everyone.
“Eight glasses per day is not the best recommendation for everyone,” said Stavros Kavouras, PhD, founding director of the Hydration Science Lab at Arizona State University. He suggested that eight glasses can be considered a bare minimum rather than a target.
The National Academy of Medicine recommends about 13 8-ounce cups of fluid per day for men and 9 cups for women. Additionally, men need about 3 cups and women need 2 cups of water from food sources, such as fruits and vegetables.
Foods That Provide Hydration
Instead of measuring every ounce of water, trial and error can help determine the right amount for you, Breyer noted. Listen to your body’s thirst signals, and check your urine:
“If you pee approximately every two to three hours, and if your urine is also light in color, looking more like lemonade and less like apple juice, then you’re almost 100% sure that you’re optimally hydrated,” said Kavouras.
Hydration needs vary depending on individual circumstances. For example, an ultramarathoner will require more water than someone with a sedentary lifestyle.
“It’s sort of a nuanced thing and maybe depends some on someone’s goals, maybe depends on any other health conditions they have,” said Breyer.
If you’re aiming to lose weight or have a specific health condition, talk to your doctor about your fluid intake.
Staying Hydrated Safely
Dehydration and overhydration can both be dangerous, but moderate increases in water intake are generally safe for most people. For instance, drinking 17 ounces of water before meals, as seen in the weight loss studies, is a practical and safe strategy.
However, increased water intake might not be suitable for everyone. For example, those with heart conditions that cause fluid retention or individuals who frequently wake up to urinate at night may need to moderate their intake, Breyer cautioned.
He recommends treating hydration as a core component of health, alongside proper nutrition, exercise, and social engagement. Keeping a water bottle nearby can make hydration part of your daily routine.
“Relying solely on your thirst and waiting to get thirsty is not the best way to stay optimally hydrated,” said Kavouras. “Having water close to you most of the day is important.”
Why Don’t We Know More About Water Intake?
More research is needed to better understand optimal hydration strategies. Kavouras emphasized that water has long been overlooked as a key nutrient in scientific studies.
“From the scientist’s perspective, I keep saying that water is one of the forgotten nutrients. It’s something that we even forgot to record and study,” he said.
Breyer shares this hope for more research.
“Water is ubiquitous, and we all consume it, and it does seem to be an important part of our health,” he said. “Understanding when you could increase fluid consumption to help aid different medical conditions outside of just routine health is an interesting question, and maybe data like this spurs interest for other researchers to do randomized trials. Maybe data like this spurs people to think about healthy lifestyles and how they can focus on their health and wellness and lead healthier lives.”