How Much Water Should You Drink in a Day?
Breaking the Eight-Glass Myth
How can you make sure you're staying hydrated? Should you rely on thirst alone, or is it best to abide by the eight-glasses-a-day rule?
The truth is, either approach will probably work just fine -- for the most part. But your fluid needs can vary, depending on your activity level, the weather, environmental conditions, and even the medications you may be taking.
Getting to know which situations are likely to increase your need for fluids can help you stay hydrated. But don't go overboard. There's no point in drinking more water than you need, just for the sake of it. At the very least, you'll end up running to the bathroom every 10 minutes. At worst, you could put yourself at risk of a life-threatening condition called hyponatremia, or water intoxication. So, how much water should you drink in a day? Read on to find out!
Too Much of a Good Thing
Under normal circumstances, a healthy body can process large amounts of water as long as it also has plenty of electrolytes, in particular, sodium. But the combination of too much water and not enough sodium can cause problems. Those at highest risk of developing hyponatremia are:
- Endurance athletes who lose large amounts of sodium through sweating and then flood their bodies with too much fluid as they try to rehydrate
- People with kidney problems
- People over 65 years of age who take multiple medications or have health conditions that compromise the body's ability to get rid of fluids or maintain adequate sodium levels
Although rare, hyponatremia can also occur as a result of unsafe crash dieting or binge beer-drinking.
So What About Those Eight Glasses?
Contrary to popular belief, there is no evidence to suggest that staying hydrated hinges on drinking eight 8-ounce glasses of water each day. And relying on the eight-glass rule may not be enough to avoid dehydration in certain circumstances.
Mild dehydration, if it occurs frequently, may increase your risk for health problems such as heartburn, constipation, kidney stones, and even kidney failure. Severe dehydration can cause your body to shut down and go into shock. So make sure you know the early warning signs of dehydration in order to take action and protect your health.
How Dehydration Happens
Mild dehydration occurs when you lose 3% to 5% of your body weight through loss of fluids (usually sweat, vomit, or diarrhea).
Heat and Exertion
If you're already low on fluids, and you exercise or do physical labor in a hot environment, you can become dehydrated in a matter of hours.
Fortunately, dehydration is unlikely to happen without triggering significant thirst, so if you feel thirsty, listen to your body and take frequent sips of water. Don't gulp down gallons, especially if you're suffering from nausea or diarrhea -- it's likely to make things worse.
Signs of Mild Dehydration
The following signs are tip-offs that you may be in the early stages of dehydration:
- Dry mouth and lips; mouth may also feel a bit gummy or sticky
- Difficulty concentrating
- Elevated heart rate
Don't ignore these clues, especially if you experience two or more at the same time.