Dehydration

What you should know about dehydration

Dehydration occurs when more water and fluids leave the body than enter it. Even low levels of dehydration can cause headaches, lethargy, and constipation.

The human body is roughly 75 percent water. Without this water, it cannot survive. Water is found inside cells, within blood vessels, and between cells.

A sophisticated water management system keeps our water levels balanced, and our thirst mechanism tells us when we need to increase fluid intake.

Although water is constantly lost 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 move water around to areas where it is needed most 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.Fast facts about dehydration

  • Around three-quarters of the human body is water.
  • The causes of dehydration include diarrhea, vomiting, and sweating.
  • Individuals more at risk of dehydration include athletes, people at higher altitudes, and older adults.
  • Early symptoms of dehydration include dry mouth, lethargy, and dizziness.

Symptoms

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.

However, it is important to note that, particularly in older adults, dehydration can occur without thirst. This is why it is important to drink more water when ill, or during hotter weather.

As the condition progresses to moderate dehydration, symptoms include:

  • dry mouth
  • lethargy
  • weakness in muscles
  • headache
  • dizziness

Severe dehydration (loss of 10-15 percent of the body’s water) may be characterized by extreme versions of the symptoms above as well as:

  • lack of sweating
  • sunken eyes
  • shriveled and dry skin
  • low blood pressure
  • increased heart rate
  • fever
  • delirium
  • unconsciousness

Symptoms in children

  • in babies – a sunken fontanel (soft spot on the top of the head)
  • dry tongue and mouth
  • irritable
  • no tears when crying
  • sunken cheeks and/or eyes
  • no wet diaper for 3 or more hours

Causes

The basic causes of dehydration are not taking in enough water, losing too much water, or a combination of both.

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 from happening. The body excretes too much water, 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. Similarly, a fever can cause an increase in sweating and may dehydrate the patient, especially if there is also diarrhea and vomiting.

Diabetes – high blood sugar levels cause increased urination and fluid loss. 

Frequent urination – usually caused by uncontrolled diabetes, but also can be due to alcohol and medications such as diuretics, antihistamines, blood pressure medications, and antipsychotics.

Burns – blood vessels can become damaged, causing fluid to leak into the surrounding tissues.

Risk factors

Although dehydration can happen to anyone, some people are at a greater risk. Those at most risk include:

  • People at 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.
  • Infants and children – most commonly due to diarrhea and vomiting.

Dehydration in older adults is also common; sometimes this occurs because they drink less water so that they do not need to get up for the toilet as often. There are also changes in the brain meaning that thirst does not always occur.

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