What causes dehydration?

Dr. Carlos F. Lerner, MD

Dehydration occurs when the body loses more water and salts than it takes in. The body naturally loses water daily through sweat, tears, breathing, urine and stool. In a healthy person, this water is replaced by drinking fluids and eating foods that contain water. When you become so sick with fever, diarrhea or vomiting, or are overexposed to the sun and do not drink enough water, dehydration occurs. Whatever the cause, dehydration should be treated as soon as possible.

It is important to take steps to avoid dehydration.

  • Drink plenty of fluids (especially when playing in the sun).
  • Schedule outdoor activities during cooler times of the day.
  • Drink appropriate fluids to help maintain the body's electrolyte balance.

In addition to dehydration, strenuous or prolonged activity during the hottest times of the day can lead to heat exhaustion or heatstroke.

Dr. Aruna V. Josyula, MD
Geriatric Medicine Specialist

There are many causes of dehydration. The most obvious one is that people do not drink enough water, but there are others. Some medications, such as diuretics, cause dehydration. An infection that leads to fever, vomiting or diarrhea can also lead to dehydration. Too much exposure to heat or too much exercise can result in the condition as well.

Trinity Health is a Catholic health care organization that acts in accordance with the Catholic tradition and does not condone or support all practices covered in this site. In case of emergency call 911. This site is educational and not a substitute for professional medical advice, always seek the advice of a qualified healthcare provider.

When the amount of fluid you lose (usually from sweat) exceeds the amount you drink, you can become dehydrated. It can cause fatigue, nausea, vomiting, headache and, in severe cases, loss of consciousness. Dehydration occurs when you lose 2 to 3 percent of your body weight in fluid. This means that if a 150-pound man loses three or more pounds during exercise, he reached a state of dehydration during that activity.

Dehydration may be caused by not drinking enough water, losing too much fluid or both. Any of the following may increase your chance of having dehydration:

  • advanced age with decreased ability to sense thirst or to concentrate urine
  • being in the sun or heat for too long, or sweating a lot, such as when you exercise
  • diseases, such as stroke, diabetes, heart problems or infections
  • medicines that cause you to lose water and salt, such as diuretics (water pills)
  • vomiting, diarrhea or fever that lasts a long time

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.