Signs, Symptoms, Causes, and Prevention of Dehydration


Dehydration occurs when more water and fluid leave the body than it enters. Even low dehydration can cause headaches, fatigue, and constipation.

The human body is made up of about 75 percent water. Without this water, it cannot survive. Water is found inside cells, inside blood vessels, and between cells.

A sophisticated water management system keeps our water levels in check, and our drying system tells us when we need to increase the amount of fluid used. Although water is constantly lost throughout the day as we breathe, sweat, urinate and excrete, we can replenish our bodies by drinking fluids. The body can also move water to areas where it is most needed when dehydration begins.

Many cases of dehydration can be easily reversed by increasing the fluid, but severe dehydration situations need immediate attention.

Quick facts about dehydration
Quick facts about dehydration

  • About three-quarters of the human body is made up of water.
  • Causes of dehydration include diarrhea, vomiting, and sweating.
  • People most at risk of dehydration include athletes, people in high places, and older adults.
  • The first signs of dehydration include dry mouth, fatigue, and dizziness.



Dehydration is easy to correct but can be worse if left untreated.

Early symptoms of dehydration include thirst, dark urine, and decreased urine production. The color of the urine is one of the best indicators of a person’s hydration level – clear urine means it is full of water and black urine means dehydration.

However, it is important to note that, especially in adults, dehydration can occur without thirst. This is why it is important to drink plenty of water when you are sick, or during hot weather.

As the condition progresses to moderate dehydration, symptoms include:

  • Dry mouth
  • Fatigue
  • Muscle weakness
  • A headache
  • Dizziness

Severe dehydration (loss of 10-15 percent body fluids) may be manifested by extreme versions of the above symptoms as well:

  • Lack of sweat
  • Eyes down
  • Wrinkled and dry skin
  • Low blood pressure
  • Heart rate increase
  • Fever
  • Delirium
  • Fainting

Symptoms in children

  • Dead fontanel (soft spot on top of head),
  • Dry tongue and mouth.
  • No tears when she cries.
  • Sunken cheeks and/or eyes.
  • No wet diaper for 3 hours or more.



The underlying causes of dehydration are not getting enough water, dehydration, or a combination of both.

Sometimes, we can’t drink enough fluids because we are too busy, have no resources or energy to drink, or are in an area where there is no drinking water (while hiking or camping, for example). Additional causes of dehydration include:

Diarrhea – is the most common cause of dehydration and related death. The large intestine absorbs water from food, and diarrhea prevents this from happening. The body produces a lot of water, which leads to dehydration.


Cleaning – leads to loss of fluid and makes it difficult to replace water by drinking it.

Sweating – the cooling system releases large amounts of water. Warm and humid weather and vigorous exercise can increase the loss of fluid due to sweating. Similarly, fever can cause increased sweating and may dehydrate a patient, especially if there is diarrhea and vomiting.

Diabetes – high blood sugar levels leading to increased urination and loss of fluid. Tips for managing summer heat in people with diabetes.

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

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

Risk factors

Risk factors

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

  • Older adults are often dehydrated.
  • People in high places.
  • Athletes, especially those who are involved in endurance sports, such as marathons, triathlons, and cycling competitions. Dehydration can interfere with athletic performance.
  • People with chronic diseases, such as diabetes, kidney disease, cystic fibrosis, alcoholism, and adrenal gland disorders.
  • Infants and children – often due to diarrhea and vomiting.

Dehydration in older adults is also common; sometimes this is because they drink less water so they do not have to get up and go to the toilet more often. There are also changes in the brain which mean that thirst does not always occur.


If dehydration is not diagnosed, it can lead to serious problems; this could include:

  • Low blood pressure – low blood pressure produces a decrease in blood pressure and a decrease in the amount of oxygen reaching the tissues; this could be life in danger.
  • Constipation – due to electrolyte imbalances.
  • Kidney problems – including kidney stones, urinary tract infections, and eventually kidney failure.
  • Heat damage – from minor cramps to heat loss or even heat stroke.


The doctor will use both physical and mental tests to determine dehydration. A patient who shows symptoms such as confusion, low blood pressure, rapid heartbeat, fever, lack of sweat, and elastic skin will generally be considered dehydrated.

Blood tests are often used to test kidney function and test for sodium, potassium, and other electrolyte levels. Electrolytes are chemicals that control the flow of water in the body and are essential for the functioning of the nerves and muscles. Urine analysis will provide very useful information to help diagnose dehydration. In dehydrated people, the urine will be darker in color and more concentrated – it contains a certain amount of compounds called ketones.

To diagnose dehydration in infants, doctors usually look for a soft spot on the skull. They may also notice a loss of sweat and specific features of muscle tone.



Prevention is the most important treatment for dehydration. Consuming too much liquid and watery foods (such as fruits and vegetables) should be enough for most people to prevent dehydration.

People should be careful about doing activities during the hottest or hottest part of the day, and anyone exercising should make the liquid filling a priority.

Since the elderly and the very young are at high risk for dehydration, special care should be given to ensure that they receive adequate fluids.