©2018 WebMD, Inc. All rights reserved. eMedicineHealth does not provide medical advice, diagnosis or treatment. See Additional Information.

Symptoms and Signs of Dehydration in Adults

Doctor's Notes on Dehydration in Adults

Dehydration is a state of fluid deficit, or loss, in the body. It happens whenever more fluid is lost than is taken in. Fluid can be lost from the body through bleeding, sweating, vomiting, urination, or diarrhea.

Dehydration can be caused by any illness that causes

  • diarrhea or vomiting,
  • excessive sweating, injury that causes bleeding, or
  • simply by not taking in enough fluid to meet the body's demands.
  • Fever can also cause the body to lose more water than usual.

The symptoms of dehydration may be mild or severe. Symptoms associated with dehydration include:

Symptoms of severe dehydration include:

  • Breathing rapidly,
  • extremely dry skin,
  • rapid heartbeat,
  • sleepiness,
  • confusion,
  • dizziness,
  • fainting,
  • sunken eyes, and
  • not urinating

Severe dehydration is a medical emergency.

Medical Author:
Medically Reviewed on 4/29/2019

Dehydration in Adults Symptoms

The signs and symptoms of dehydration in adults range from minor to severe.

Mild to moderate dehydration may include the following:

The above symptoms may quickly worsen and indicate severe dehydration with signs and symptoms are developing; severe dehydration may include the following:

  • Severely decreased urine output or no urine output. The urine, if any, produced is concentrated and a deep yellow or amber color.
  • Dizziness or lightheadedness that does not allow the person to stand or walk normally.
  • Blood pressure drops when the person tries to stand after lying down (low blood pressure or orthostatic hypotension)
  • Rapid heart rate
  • Fever
  • Poor skin elasticity (skin slowly sinks back to its normal position when pinched)
  • Lethargy, confusion, or coma
  • Seizure
  • Shock

Dehydration in Adults Causes

Many conditions may cause rapid and continued fluid losses and lead to dehydration.

  • Fever, heat exposure, too much exercise, or work-related activity
  • Vomiting, diarrhea, and increased urination due to infection
  • Diseases such as diabetes
  • The inability to seek appropriate water and food (an infant or disabled person, for example)
  • An impaired ability to drink (someone in a coma or on a respirator, or a sick infant who cannot suck on a bottle are common examples)
  • No access to safe drinking water
  • Significant injuries to skin, such as burns or mouth sores, severe skin diseases, or infections (water is lost through the damaged skin)

In addition to drinking water, the body also needs replacement of electrolytes (for example, potassium and sodium) lost with the above mentioned conditions, so drinking water without electrolyte replacement may not complete the balance of water and electrolytes the body has lost. Some symptoms (see below) may remain if this balance is not restored.

Dehydration Causes, Symptoms & Tips to Stay Hydrated Slideshow

Dehydration Causes, Symptoms & Tips to Stay Hydrated Slideshow

The majority of the body is made up of water with up to 75% of the body's weight due to H2O. Most of the water is found within the cells of the body (intracellular space). The rest is found in the extracellular space, which consists of the blood vessels (intravascular space) and the spaces between cells (interstitial space).


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.