Dehydration (from the Greek hydor (water)) and the Latin prefix de- (indicating deprivation, removal, and separation) occurs when more water and fluids are exiting the body than are entering the body. With about 75% of the body made up of water found inside cells, within blood vessels, and between cells, survival requires a rather sophisticated water management system.
Luckily, our bodies have such a system, and our thirst mechanism tells us when we need to increase fluid intake. Although water is lost constantly throughout the day as we breathe, sweat, urinate, and defecate, we can replenish the water in our body by drinking fluids. The body can also shift water around to areas where it is more needed if dehydration begins to occur.
Most occurrences of dehydration can be easily reversed by increasing fluid intake, but severe cases of dehydration require immediate medical attention.
Causes of dehydration
The Institute of Medicine recommends daily fluid intake of 13 cups (3 liters) for adult men (as total beverages, including drinking water) and 9 cups (2.2 liters) for adult women.
The immediate causes of dehydration include not enough water, too much water loss, or some combination of the two.
Sometimes it is not possible to consume enough fluids because we are too busy, lack the facilities or strength to drink, or are in an area without potable water (while hiking or camping, for example). Additional causes of dehydration include:
- Diarrhea - the most common cause of dehydration and related deaths. The large intestine absorbs water from food matter, and diarrhea prevents this function, leading to dehydration.
- Vomiting - leads to a loss of fluids and makes it difficult to replace water by drinking it.
- Sweating - the body's cooling mechanism releases a significant amount of water. Hot and humid weather and vigorous physical activity can further increase fluid loss from sweating.
- Diabetes - high blood sugar levels cause increased urination and fluid loss. Tips for handling summer heat for people with diabetes.
- Frequent urination - usually caused by uncontrolled diabetes, but also can be due to alcohol and medications such as diuretics, antihistamines, blood pressure medications, and anti-psychotics.
- Burns - water seeps into damaged skin and the body loses fluids.
Who is at risk of dehydration?
Although dehydration can happen to anyone, some people are at a greater risk. Those highest at risk include:
- People in higher altitudes
- Athletes, especially those in endurance events such as marathons, triathlons, and cycling tournaments. Dehydration can undermine performance in sports, as this article explains.
- People with chronic illnesses such as diabetes, kidney disease, cystic fibrosis, alcoholism, and adrenal gland disorders
- Older adults, infants, and children. Dehydration in elderly people can be explained by brain malfunction, a study revealed. An article explains how drinking more water improved the health of elderly people.
Symptoms of dehydration
The first symptoms of dehydration include thirst, darker urine, and decreased urine production. In fact, urine color is one of the best indicators of a person's hydration level - clear urine means you are well hydrated and darker urine means you are dehydrated.
As the condition progresses to moderate dehydration, symptoms include:
- Dry mouth
- Few or no tears when crying
- Weakness in muscles
Severe dehydration may be characterized by extreme versions of symptoms mentioned above as well as:
- Lack of sweating
- Sunken eyes
- Shriveled and dry skin
- Sunken fontanels (soft spots) in babies
- Low blood pressure
- Increased heart beat
On the next page we look at the diagnosis of dehydration, the available treatments and how dehydration can be prevented.