About two-thirds of your body weight is water. All your cells need water to work. Water is also the base for all your different body fluids, including saliva, blood, urine, sweat, and joint fluid. No living thing can survive without water. How do you know if you’re drinking enough?
Your body loses water when you sweat, go to the bathroom, and even when you just breathe out. So, you need to drink enough water to replace what you lose. When you don’t drink enough water, you can become dehydrated.
Signs that you’re getting dehydrated include feeling very thirsty and having headaches. Your mouth or skin may feel very dry. And your urine may get darker because your body is trying to conserve water. Drinking fluids should be enough to relieve mild dehydration.
If dehydration becomes severe, it can cause confusion, fainting, an inability to urinate, and rapid heartbeat and breathing. At this point, it can be life-threatening, and you should seek medical help fast. Drinking liquids may not be enough to replenish your body’s fluids. You may need to be given fluids intravenously—through a needle or tube inserted into a vein.
Recent NIH-funded research suggests that avoiding dehydration may not be the only reason to make sure you drink enough fluids. Dr. Natalia Dmitrieva, a heart researcher at NIH, has studied the long-term effects of not drinking enough water. In one study, her team found that middle-aged people who were not adequately hydrated were more likely to develop chronic diseases. The diseases included heart failure, diabetes, chronic lung disease, and dementia.
These people were also more likely to age faster and die younger. So, staying well hydrated might help you stay healthier as you get older.
The best way to avoid dehydration is to make sure you drink enough fluids every day. Ideally, you should get your fluids from water or other low-calorie beverages, such as plain coffee or tea, or sparkling or flavored waters. Nutritional beverages, such as milk or milk alternatives, or 100% vegetable juice, are also good options. Relying on soda, sports drinks, or other sugary beverages for most of your fluids can add many calories to your diet, and they have little nutritional value.
How much you should drink each day depends on many factors, including your age, where you live, and your body weight. And your body doesn’t always lose water at the same rate. For instance, when you exercise or are active in hot weather, you sweat more and so need to drink more. But experts generally recommend drinking around 9 cups of fluids a day for women and 13 cups for men on average.
Certain diseases, like diabetes or chronic kidney disease, and some medicines can make you urinate more often. You also lose a lot of water when you throw up or have diarrhea or a fever. In these cases, you need to drink more water to avoid getting dehydrated.