How to prevent dehydration in hot weather

Lethargic? Fuzzy-headed? The remedy may be as close as your kitchen tap.

Published: July 03, 2014 04:00 PM

The retired schoolteacher brought to my office by her daughter had sunken eyes, a parched mouth and tongue, and poor skin elasticity. “She tends to fall a lot and gets confused,” her daughter privately confided in me. “And she’s not as alert as she was. I think she might be depressed.”

She was clearly depressed and mildly confused—but she also had all of the signs of chronic dehydration. It didn’t take long to figure out why. The woman had recently moved to an assisted living facility and admitted that she skipped meals when she was too tired to make the 10-minute walk to the facility’s dining room. And she often spent entire days in her room watching TV. On those days, her only fluid intake was the orange juice and coffee she consumed at breakfast and a few sips of water when she took her medication at night.

Why water matters

Photo: somchaij

Without water, most of us would perish within a week. It accounts for up to 75 percent of our body weight, and even at rest, we lose about 4 to 8 cups per day through urination, defecation, and breathing. Hot summer days, exercise, fever, vomiting, or diarrhea increase those losses many-fold.

In other words, without adequate fluid intake, it’s very easy to become dehydrated. It’s a condition not to be taken lightly: Complications from chronic dehydration include confusion, constipation, heartburn, fainting, fatigue, skin allergies, muscle aches, and joint pain.

The condition can also increase the risk of blood clots, infections, and kidney stones. Some studies have found that as little as a 1 to 3 percent drop in body weight due to water loss can result in cognitive impairment and confusion. And if untreated over a period of time, dehydration can occasionally lead to a potentially life-threatening slowdown of the body’s circulation and cellular functioning.

Find out what your best options are for urgent medical care. And find out if your hospital is really as safe as you think.

The body, in its wisdom, has vigorous defenses against dehydration. Even small amounts of water loss result in increased concentration of minerals and proteins in our bloodstream. That, in turn, is sensed by the brain’s pituitary gland, which sends a signal to the kidneys telling them to concentrate the urine to conserve water. (In fact, one unmistakable sign of dehydration is urine that’s darker than usual.) Another brain center sends a signal that results in the sensation of thirst, prompting us to drink something.

Unfortunately, those defense mechanisms against dehydration deteriorate with age, making older people increasingly vulnerable to water loss—even normal everyday water loss. They don’t perceive thirst as readily as when they were younger, and their kidneys’ ability to conserve water by concentrating urine also declines.

Drink up, starting now

The only way to prevent dehydration is to be aware that it can happen to you no matter what your age. To offset fluid loss during a normal day of relative inactivity takes a minimum of about 6 to 8 cups of fluids. That amount may sound formid­able, but it’s really not if you take into account that virtually everything we eat contains water, especially fruits and vegetables. But even meat, fish, and poultry contain some liquid. Add some juice, yogurt, and soup, and the daily goal can easily be met. Exercise, hot weather, and illness require additional fluids, often several times what you normally need. In some instances when vomiting and diarrhea are severe, hospitalization and intravenous fluids may be required.

And that’s how we treated the schoolteacher. After three days of gradual intravenous rehydration in the hospital, she was discharged looking and feeling like a new person, bright and alert. Her daughter got her a room closer to the dining area and a hip flask as a reminder to take a swig (of water!) every hour, whether she thought she needed it or not.

Marvin Lipman, M.D.

Chief Medical Adviser and Medical Editor
Editor's Note:

This article also appeared in the August 2014 issue of Consumer Reports on Health.

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