Drink more Water, but What's the Right Amount?

The reason may be something most people would not expect: dehydration.

Serious athletes are not the only ones at risk of becoming dehydrated. In fact, if you talk to emergency medical technicians after a professional sporting event, they will tell you that they mainly end up transporting spectators.

So what are the warning signs that you haven't had enough water to drink?

The symptoms of dehydration depend on the individual, which can make them tricky to spot.

Most people will feel weak or faint, symptoms that may be accompanied by headache or nausea. Some people get cramps, often in their calves or thighs, a result of the low salt levels that can be triggered by insufficient fluid intake.

You may feel exhausted, almost as if you have a fever, even if you don't have a high temperature. That's why one colloquial name for dehydration is summer flu.

All of which raises a question: How much water is enough?

Unfortunately, there is no one-size-fits-all answer. You may have heard that everyone should drink eight glasses of water a day, but there is no solid research to back that up. And there is no consensus in the medical community on the optimal amount.

What doctors do agree on is a piece of common sense: Everyone should "drink to thirst." Basically, if you're thirsty, you should drink, perhaps a bit past the point of feeling satisfied.

Of course, there is a little more to it than that. As you age, your body's ability to sense that it needs water degrades. So older patients — especially very elderly ones or older athletes — are at particular risk. People in these categories may need to drink more than their thirst level is telling them.

Drinking alcohol can also complicate matters. Alcohol inhibits some of the hormones that help you feel thirsty, and it causes you to lose even more fluid through urination. Especially if you're drinking alcohol in the heat, I recommend drinking one glass of water for every alcoholic beverage.

There is one tried-and-true way to know if you are sufficiently hydrated: Check the color of your urine. It should be a medium to light-colored yellow, not dark.

For non-elite athletes — weekend warriors and people who exercise three days a week on average — drinking any time you're thirsty is a good enough guideline. Staying hydrated is a bit more complicated for a more elite or endurance athlete — for example, someone who is training for competition on most days of the week, regularly runs 10 more miles a day, or plays three hours of tennis daily.

If you are this active, you should drink about three liters of water on the days you are exercising. One test is to weigh yourself before and after exercise. You don't want to lose more than 2% of your body weight during exercise, or your performance will suffer. For a 150-pound athlete, that means you would not want to lose more than three pounds during your workout or competition.

An extremely active person who trains daily — such as a marathoner — should have up to six liters of water a day. For people who are drinking this much, we recommend a 3/2 ratio of sports drink to water. If you don't want to blend the two, then drink three 16-ounce sports drinks to every two bottles of water.

Another option is to add sodium packets to your water, as recommended by your doctor.

Paradoxically, overhydration can be a problem for endurance athletes. In the middle of a tough workout, they sometimes think that drinking water can help with their fatigue and aching muscles. Then they can overdo it and strip the body of necessary electrolytes.

To prevent that outcome, be careful to drink plenty of fluids the day before (pre-hydrate), as well as during, your long workouts.

I am often asked whether sports drinks are OK for kids. Many kids love them because they taste sweet and often have caffeine. But I recommend serving a half-and-half mixture of water and sports drink, and I don't recommend caffeinated drinks like Red Bull or Monster at all for children younger than 12.

If your child hates to drink water, try mixing in other flavors, like a splash of 100% fruit juice or a twist of lemon. Sometimes, even having your kids pick out their own water bottles can make a big difference. For them, a sparkly water bottle helps make water cool.

Awareness is the first step toward preventing dehydration. It doesn't matter if you like your water hot or cold, or mixed with lemon or a flavor packet like Crystal Lite. Just don't leave home without your water bottle: Sip from it and refill it all day.

And if you feel thirsty, listen to your body!

Melissa Leber MD, FACEP, is Assistant Professor of Orthopedics and Emergency Medicine at Icahn School of Medicine at Mount Sinai Hospital, and Director of Emergency Department Sports Medicine.