What's in this article?
Dehydration occurs when you use or lose more fluid than you take in, and your body doesn’t have enough water and other fluids to carry out its normal functions. If you don’t replace lost fluids, you will get dehydrated.
Common causes of dehydration include vigorous exercise, especially in hot weather; intense diarrhea; vomiting; fever or excessive sweating. Not drinking enough water during exercise or in hot weather even if you’re not exercising also may cause dehydration. Anyone may become dehydrated, but young children, older adults and people with chronic illnesses are most at risk.
You can usually reverse mild to moderate dehydration by drinking more fluids, but severe dehydration needs immediate medical treatment. The safest approach is preventing dehydration in the first place. Keep an eye on how much fluid you lose during hot weather, illness or exercise, and drink enough liquids to replace what you’ve lost.
Dehydration facts
- The body needs water to function.
- Dehydration occurs when water intake is less than water loss.
- Symptoms range from mild to life-threatening.
- The young and the elderly are especially susceptible to dehydration.
Causes of dehydration
You can become dehydrated if you lose too much fluid, do not drink enough water or fluids, or both.
Your body may lose a lot of fluid from:
- Sweating too much, for example, from exercising in hot weather
- Fever
- Vomiting or diarrhea
- Urinating too much (uncontrolled diabetes or some medications, like diuretics, can cause you to urinate a lot)
You might not drink enough fluids because:
- You do not feel like eating or drinking because you are sick
- You are nauseated
- You have a sore throat or mouth sores
Older adults and people with certain diseases, such as diabetes, are also at higher risk for dehydration.
Symptoms of dehydration
Dehydration can be mild, moderate or severe, depending on how much of your body weight is lost through fluids.
Two early signs of dehydration are thirst and dark-coloured urine. This is the body’s way of trying to increase water intake and decrease water loss.
Other symptoms may include:
- dizziness or light-headedness
- headache
- tiredness
- dry mouth, lips and eyes
- passing small amounts of urine infrequently (less than three or four times a day)
Dehydration can also lead to a loss of strength and stamina. It’s a main cause of heat exhaustion.
You should be able to reverse dehydration at this stage by drinking more fluids.
If dehydration is ongoing (chronic), it can affect your kidney function and increase the risk of kidney stones. It can also lead to muscle damage and constipation.
Risk factors of dehydration
Anyone can become dehydrated if they lose too many fluids. But certain people are at greater risk, including:
- Infants and children. Infants and children are especially vulnerable because of their relatively small body weights and high turnover of water and electrolytes. They’re also the group most likely to experience diarrhea.
- Older adults. As you age, you become more susceptible to dehydration for several reasons: Your body’s ability to conserve water is reduced, your thirst sense becomes less acute, and you’re less able to respond to changes in temperature. What’s more, older adults, especially people in nursing homes or living alone, tend to eat less than younger people do and sometimes may forget to eat or drink altogether. Disability or neglect also may prevent them from being well nourished. These problems are compounded by chronic illnesses such as diabetes, dementia, and by the use of certain medications.
- People with chronic illnesses. Having uncontrolled or untreated diabetes puts you at high risk of dehydration. But other chronic illnesses, such as kidney disease and heart failure, also make you more likely to become dehydrated. Even having a cold or sore throat makes you more susceptible to dehydration because you’re less likely to feel like eating or drinking when you’re sick. A fever increases dehydration even more.
- Endurance athletes. Anyone who exercises can become dehydrated, especially in hot, humid conditions or at high altitudes. But athletes who train for and participate in ultramarathons, triathlons, mountain climbing expeditions and cycling tournaments are at particularly high risk. That’s because the longer you exercise, the more difficult it is to stay hydrated. During exercise, your body may lose more water than it can absorb. With every hour you exercise, your fluid debt increases. Dehydration is also cumulative over a period of days, which means you can become dehydrated with even a moderate exercise routine if you don’t drink enough to replace what you lose on a daily basis.
- People living at high altitudes. Living, working and exercising at high altitudes (generally defined as above 8,200 feet, or about 2,500 meters) can cause a number of health problems. One is dehydration, which commonly occurs when your body tries to adjust to high elevations through increased urination and more rapid breathing — the faster you breathe to maintain adequate oxygen levels in your blood, the more water vapor you exhale.
- People working or exercising outside in hot, humid weather. When it’s hot and humid, your risk of dehydration and heat illness increases. That’s because when the air is humid, sweat can’t evaporate and cool you as quickly as it normally does, and this can lead to an increased body temperature and the need for more fluids.
How is dehydration treated?
As is often the case in medicine, prevention is the important first step in the treatment of dehydration. (Please see the home treatment and prevention sections.)
Fluid replacement is the treatment for dehydration. This may be attempted by replacing fluid by mouth, but if this fails, intravenous fluid (IV) may be required. Should oral rehydration be attempted, frequent small amounts of clear fluids should be used.
Clear fluids include most things you can see through.
- Water (please note that water alone is not necessarily safe to use in infants and can lead to significant electrolyte problems. For this reason, Pedialyte or other balanced electrolyte solutions should be used.
- Clear broths
- Popsicles
- Jell-O
- Other replacement fluids that may contain electrolytes (Pedialyte, Gatorade, Powerade, etc.)
Decisions about the use of intravenous fluids depend upon the health care professional’s assessment of the extent of dehydration, the ability for the patient to drink fluids by mouth, and the ability for the patient to recover from the underlying cause.
The success of the rehydration therapy can be monitored by urine output. When the body is dry, the kidneys try to hold on to as much fluid as possible, urine output is decreased, and the urine itself is concentrated. As treatment occurs and if it is successful, the kidneys sense the increased amount of fluid within the intravascular space and urine output increases.
Medications may be used to treat underlying illnesses and to control fever, vomiting, or diarrhea.
To prevent dehydration
- Drink plenty of fluids every day, even when you are well. Drink more when the weather is hot or you are exercising.
- If anyone in your family is ill, pay attention to how much they are able to drink. Pay close attention to children and older adults.
- Anyone with a fever, vomiting, or diarrhea should drink plenty of fluids. DO NOT wait for signs of dehydration.
- If you think you or someone in your family may become dehydrated, call your provider. Do this before the person becomes dehydrated.
