The general recommendations for water intake are a good starting point, but your individual needs can vary based on other factors, such as age and activity level. Here are some of the factors that influence how much water you need.
When you sweat during exercise or on a hot summer day, you need to replace the fluids you’ve lost by drinking more water.
The intensity and duration of exercise affect how much you sweat and your subsequent fluid needs. The temperature also affects how much you sweat, as does your body weight and composition. You don’t have to visibly sweat to become dehydrated, which can happen while swimming in a pool or lake, or skiing on a winter day.
Calculating exact hydration losses from physical activity is complicated because people sweat at different rates. People of the same gender and weight, and with similar diets, will sweat different amounts in the exact same conditions, thus need different amounts of fluid.
Age
Children and teens need proportionally more water than adults relative to their body size, especially during growth spurts and active play, says Derocha.
Older adults may experience a reduced sense of thirst and may need to be more mindful about drinking regularly, even if they don’t feel thirsty. Research has found that chronic dehydration is a common problem in adults. In older adults, the chronic dehydration rate in the United States ranges from 17 to 28 percent.
“Dehydration can exacerbate or make other health conditions worse,” says Kalisha Bonds Johnson, PhD, RN, an assistant professor at Emory University’s Nell Hodgson Woodruff School of Nursing in Atlanta. “Dehydration or inadequate hydration can lead to confusion, poor blood pressure regulation, and poor kidney health. The effects of dehydration on the kidneys can result in a urinary tract infection, which can lead to delirium and also exacerbate symptoms of dementia until corrected.”
Body Weight and Birth Sex
Hydration needs are influenced by the surface area of the body, metabolic rate, and body weight.
“Muscle tissue is about 75 percent water, while fat tissue is only about 10 percent water,” says Derocha. “As a result, as body weight increases, fluid needs increase.”
Compared with people born female, those born male generally need more fluid to support their increased body mass, lower average body fat, and increased calorie burn each day. Men typically sweat more than women.
Pregnancy and Nursing
Pregnant women require additional fluids to maintain amniotic fluid levels, increase blood volume, and keep the baby growing steadily.
If you’re nursing a growing baby, you need to drink more fluids so that your body can make enough milk. Derocha says that a nursing mother typically needs about 16 cups (3.8 liters) per day total — with about 3 cups of that specifically to support milk production.
Diet Quality
The foods you eat affect your hydration and the amount of fluid you need to drink. If you eat ample fruits and veggies each day, you don’t need to drink as much water. Some fruits and vegetables have higher water content than others. Watermelon and spinach, for example, are especially hydrating, as they are almost 100 percent water by weight. Soup is another fluid-rich food that can help you meet your target water intake.
If your fruit and vegetable intake is low on a given day, a few extra glasses of water will compensate. Drinking extra water when drinking alcohol is also a good idea, as alcohol is a diuretic and can make you dehydrated.
