What Causes Dehydration?

Medically reviewed by Mark R Laflamme, MD on February 3, 2016 Written by April Kahn

Dehydration takes place when your body loses more fluid than you drink. The most common cause of water loss from the body is excessive sweating. The suggested amount of water to drink is eight to 10 glasses per day for an average, not active... Read More

Dehydration takes place when your body loses more fluid than you drink. The most common cause of water loss from the body is excessive sweating.

The suggested amount of water to drink is eight to 10 glasses per day for an average, not active person. Individuals on the go, athletes, and people exposed to high temperatures should increase their water intake to avoid dehydration.

When too much water is lost from the body, the organs, cells, and tissues fail to function as they should, which can lead to dangerous complications. If dehydration isn’t corrected immediately, it could cause shock. Dehydration can be mild or severe. Mild dehydration can usually be treated at home, whereas severe dehydration has to be treated in a hospital or emergency care setting.

Dehydration Risk Factors

Athletes exposed to direct sun aren’t the only ones at risk for dehydration. In fact, bodybuilders and swimmers are among the athletes that most commonly develop the condition. This is because in these sports, drinking is discouraged during training sessions or before competitions, which can cause self-induced dehydration. And, strange as it may seem, it’s possible to sweat in water. Swimmers lose a lot of sweat when swimming.

Some people are at a higher risk of developing dehydration than others, including:

  • workers exposed to excessive amounts of heat (for example, welders, landscapers, construction workers, and mechanics)
  • seniors
  • individuals with chronic illnesses
  • athletes (especially runners, cyclists, and soccer players)
  • infants and young children
  • people who reside in high altitudes

How Does Dehydration Develop?

Your body regularly loses water through sweating and urination. If the water isn’t replaced, you become dehydrated. Dehydration is caused by any situation or condition that causes the body to lose more water than usual.


Sweating is part of your body’s natural cooling process. When you become hot, your sweat glands activate to release moisture from your body in an attempt to cool it off. The way this works is by evaporation. As a drop of sweat evaporates from your skin, it takes a small amount of heat with it. The more sweat you produce, the more evaporation there is, and the more you are cooled off. Sweating also hydrates your skin and maintains the balance of electrolytes in your body. The fluid you sweat is composed mainly of salt and water. Excessive sweating can cause dehydration since you lose a large amount of water. The technical term for excessive sweating is hyperhidrosis.


Illnesses that cause continuous vomiting or diarrhea can result in dehydration. This is because vomiting and diarrhea can cause too much water to be expelled from your body. Important electrolytes are also lost through these processes. Electrolytes are minerals used by the body to control the muscles, blood chemistry, and organ processes. These electrolytes are found in blood, urine, and other fluids in the body. Vomiting or diarrhea can impair these functions and cause severe complications such as stroke and coma.


If you have a fever, your body loses fluid through your skin’s surface in an attempt to lower your temperature. Often, fever can cause you to sweat so much that if you don’t drink to replenish, you could end up dehydrated.


Urination is the body’s normal way to release toxins from your body. Some conditions can cause chemical imbalances, which can increase your urine output. If you don’t replace the fluid lost through excessive urination, you run the risk of developing dehydration.

What Are the Symptoms of Dehydration?

The symptoms of dehydration differ depending on whether the condition is mild or severe. Symptoms of dehydration may begin to appear before total dehydration takes place.

Symptoms of mild to moderate dehydration include:

  • sleepiness
  • dry mouth
  • increased thirst
  • decreased urination
  • less tear production
  • dry skin
  • constipation
  • dizziness
  • lightheadedness
  • headache

In addition to the symptoms of mild dehydration, severe dehydration is likely to cause the following:

  • excessive thirst
  • lack of sweat production
  • low blood pressure
  • rapid heart rate
  • rapid breathing
  • fever
  • sunken eyes
  • shriveled skin
  • dark urine

Symptoms of severe dehydration are a real medical emergency and should be treated by a medical professional immediately.

Medical Emergency

Children and seniors should be treated immediately, even if they’re experiencing symptoms of mild dehydration.

If a person in any age group develops the following symptoms, seek emergency care:

  • severe diarrhea
  • blood in the stool
  • diarrhea for three or more days
  • inability to keep fluids down
  • disorientation

How Is Dehydration Diagnosed?

Before beginning any tests, your doctor will go over any symptoms you have to rule out other conditions. After taking your medical history, the doctor will check your vital signs, including your heart rate and blood pressure. Low blood pressure and rapid heart rate will indicate dehydration.

A blood test may be used to check the level of electrolytes, which can help indicate fluid loss. A blood test may also be used to check your body’s level of creatinine. This helps your doctor determine how well your kidneys are functioning.

urinalysis is an exam that uses a sample of urine to check for the presence of bacteria and electrolyte loss. Your doctor can also check for dehydration by checking the color of your urine.

Strategies to Treat Dehydration

Treatments for dehydration include rehydrating methods, electrolyte replacement, and treating diarrhea or vomiting, if needed.


Rehydration methods include fluid replacement by drinking or IV. Drinking may not be possible for people suffering from diarrhea or vomiting, so fluids will be given intravenously. To do this, your doctor inserts a small IV tube in a vein in the arm. The solution provided through the IV is often a mix of water and electrolytes.

For those able to drink, the doctor will suggest drinking water along with an electrolyte-containing rehydration drink such as Gatorade or a similar sports drink. Children with dehydration are often directed to drink Pedialyte.

Homemade Rehydration Solution

If a sports drink isn’t available, you can make your own rehydration solution using:

  • 1/2 teaspoon salt
  • 6 teaspoons of sugar
  • 1 liter of water

Be absolutely certain that you are using an accurate measurement. Using too much salt or sugar can be dangerous.

Things to Avoid

Don’t treat yourself by drinking soda, overly sweet drinks, or caffeine. These drinks can worsen dehydration.

Potential Complications of Untreated Dehydration

Untreated dehydration can lead to life-threatening complications, such as:

  • heat exhaustion
  • heat cramps
  • heatstroke
  • seizures due to electrolyte loss
  • low blood volume
  • kidney failure
  • coma

How Can I Prevent Dehydration?

If you’re ill, increase your fluid intake, especially if you’re vomiting or having diarrhea constantly. If you can’t hold down liquids, consult your doctor.

If you’re going to exercise or play sports, drink 1 to 3 cups of water before beginning. At regular intervals during the workout, replace your fluids.

Dress cool in hot months and avoid being out in direct heat if you can avoid it.

Even if you aren’t active, drink the recommended amount of fluids.

Medically reviewed by Mark R Laflamme, MD on February 3, 2016 Written by April Kahn

18 possible conditions

  1. Image source
  2. Image source

This feature is for informational purposes only and should not be used to diagnose. Please consult a healthcare professional if you have health concerns.

Medically reviewed by Mark R Laflamme, MD on February 3, 2016 Written by April Kahn