Mistake #1: Drinking Water During Your Workout, But Not Before
Even if you sip on something regularly while you’re at the gym, you may be prone to headaches if you haven’t hydrated ahead of time, too. You should aim to drink at least eight ounces of water about half an hour before you exercise.
Mistake #2: Insisting on Eight Glasses a Day
Forget that… The Institute of Medicine actually recommends 11.4 cups per day, although hydration needs vary from person to person. The exact amount of Water you need is dependent on your size and weight. And since you can also get water from foods like fruits and veggies (an apple, for instance, can provide an entire cup of water), you may not need to guzzle as much if you’re eating water-rich meals and snacks. In general, though, if you take your your weight and divide it by two, that should give you roughly the number of ounces of water you need in a day.
Mistake #3: Avoiding Drinks Like Coffee and Tea
It’s a commonly held belief that coffee and tea are dehydrating because of their caffeine content—but that’s a myth, “While the caffeine in coffee and tea can be a diuretic—which causes fluid loss—the fluid in them typically makes up for it.” So your daily Starbucks habit is still better than sipping on nothing. BUT do limit the amount during and towards the end of the day.
Mistake #4: Hydrating Too Infrequently
If you feel thirsty, then yes, you should probably drink water. Same goes for when you’re exercising or it’s hot outside.these aren’t the only times when you need to rehydrate, “You also need to hydrate while you’re sitting at your desk at work, not just at the gym,” be creative by putting post it notes on your computer, in your car or places at home to remind you.
Ref’s: ‘Institute of medicine’