Your body is made up of 10 to 12 gallons of water, and every part of your body needs water to function properly. When you're thirsty, water should be your first beverage choice. It is not necessary to drink before bed unless you're thirsty or haven't met your daily fluid needs.
How much water you need depends on your age, gender, body size, activity, health issues and climate. To prevent dehydration, you need a minimum of 8 cups to 12 cups of water a day. In general, Clemson Cooperative Extension says, you need 1 quart of water for every 50 pounds of body weight, or 3 quarts for a 150-pound person. You know you're drinking enough if you're not thirsty and your urine is clear or slightly yellow.
Water After Exercise
If you exercise in the evening, you may need to drink water before bed. Like your daily water needs, how much you require after exercise varies. Weigh yourself before and after you exercise and drink two to three 8-ounce cups of water for every pound you lost in sweat. For example, if you lost 2 pounds, drink 4 cups to 6 cups of water before bed. Hydration after exercise improves nutrient distribution to your cells and helps strengthen muscles.
Water and Alcohol
Alcohol does not count toward your daily fluid needs, and since it's a diuretic, imbibing it actually increases your need for water. If you drink an alcoholic beverage in the evening, drinking water before bed may help prevent hangover symptoms caused by dehydration. Keeping a glass of water at your bedside to drink during your restless night of sleep may also help you rehydrate.
Tips for Getting Your Fill
The only downside to drinking water before bed is that you may be making frequent trips to the bathroom throughout the night, which could disrupt your sleep. Instead, aim to drink enough water throughout the day rather than chugging a few glasses before bed. In the morning, while you're waiting for your coffee to brew, drink your first glass of water. Drink another glass with breakfast, and with each meal and snack throughout the day. Fill a water bottle to drink while driving in the car, running errands and sitting at your desk at work. Drink before, during and after your workout.