Who’s at risk of dehydration?

Water is more than just a great thirst quencher. And it’s more than just a great way to cool off on a hot day.

Did you know that more than two-thirds of human body weight is water? All our body fluids contain a balance of water, sugar and salts, which is essential for normal body function and health. But we lose water and can become dehydrated.




Dehydration due to diarrhea or vomiting

Although dehydration can happen to anyone, some people are at a greater risk, including travelers, older adults and children. Travelers may be at risk of dehydration if they contract illnesses such as traveller’s diarrhea. For more information on what to do about dehydration while travelling, please visit our Travel section.

Children are more likely than adults to become dehydrated because of their smaller size and their metabolism, which uses up water and electrolytes more quickly. Also, because their immune systems are less developed and they’re in closer contact with their environment and other children, they’re more susceptible to stomach flu that lead to diarrhea, vomiting and associated dehydration.

In general, the elderly are more susceptible to dehydration because they have less water in their bodies than younger people. This also means that the onset of the symptoms of dehydration can happen more quickly. Additionally, elderly people may not notice that they are dehydrated, especially if they are taking medication or have other impairments such as dementia.

To prevent dehydration due to diarrhea or vomiting, be aware of fluid losses when you’re sick, and make sure you drink enough to replace what is lost. Many kinds of drinks and foods can replace lost water, but you should know that sweet drinks like juices and sodas are absorbed more slowly because of their sugar content. Sports drinks and sodas may also contain caffeine, which is dehydrating.

Dehydration due to heavy sweating

Sweating is a normal body process. It helps the body to cool down and maintain its temperature by allowing moisture to evaporate from the skin. This moist (or sweat) is mostly composed of the body’s water and various amounts of electrolytes. While most people naturally drink enough to replenish lost fluids during normal conditions, other conditions are more prone to dehydration due to heavy sweating. Among them:

  • Hot or dry environment
  • Strenuous/vigorous, prolonged exercise
  • Fever

Hot or dry environment

Weather is often top of mind when we think about traveling. However, did you know that many places in Canada have a high number of extreme heat events? Whether you are performing outdoor activities or working in the heat, overexposure to extreme temperatures can put your health at risk. Heat illnesses (such as dehydration) can affect you quickly, and can lead to serious health conditions. Remember that thirst is not a good indicator of dehydration. The most important thing is to keep cool and hydrated.

Strenuous/vigourous, prolonged exercise

Fluid loss in endurance activities can be very significant. Most people lose as much as 1-2 L of fluid during 1 hour of exercise and athletes can lose even more! Being active comes with an increase need of fluid intake due to the fluids lost through sweat. Not drinking enough to replace sweat losses can quickly lead to dehydration.


A fever is a temporary increase in your body temperature above its normal range, often due to an illness. It may therefore be accompanied by the same body processes of heat dissipation such as it occurs with vigorous exercise or exposure to warm temperatures. Depending on what is causing the fever, symptoms may include sweating which can lead to dehydration. Children are more prone to dehydration than adults because they can lose relatively more fluid quickly.

What are the signs and symptoms of dehydration?

Dehydration may produce a variety of symptoms.

Recognize the signs and symptoms of dehydration

  • Few or no tears when crying
  • Dry, sticky mouth and tongue
  • Fatigue or feeling sleepy; inactivity in children
  • Irritability
  • Headache, dizziness or light-headedness

Contact a physician if you or your child show signs of severe dehydration including symptoms of shock, inability to drink, increased thirst, markedly decreased or absent urine output, sunken eyes, swelling of the feet or lower legs and/or bloody or mucus-like stools.

What is

Dehydration due to diarrhea and vomiting.
Who is at risk?
What are the signs and symptoms of dehydration?

What is

Gastroenteritis, also called stomach flu, is a
common cause of diarrhea and vomiting in children.


Don’t let traveler’s diarrhea ruin your vacation!
Learn to recognize it and what to do about it.