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Symptoms and Signs of How Do You Know If a Child Is Dehydrated?

Doctor's Notes on Dehydration in Children

Dehydration is when the body loses too much water and electrolytes (minerals in the blood that support body functions). Dehydration in children may be causes by any condition that causes the body to lose too much fluid and electrolytes, such as fever, sweating, diarrhea, or vomiting. Children who have an illness also may become dehydrated if it is hard for them to drink fluids.

Signs and symptoms of dehydration in children include thirst, lethargy, dry mouth, sunken eyes, dry and cool skin, drowsiness, dizziness, ore irritability. In babies, associated symptoms can include a sunken appearance to the soft spot (fontanelle) on the head or fewer soaked diapers than normal. Older children may urinate less than normal and have dark urine.

Medical Author:
Medically Reviewed on 3/11/2019

Dehydration in Children Symptoms

Be concerned if your child has an excessive loss of fluid by vomiting or diarrhea, or if the child refuses to eat or drink.

Signs of dehydration include:

  • Sunken eyes
  • Decreased frequency of urination or dry diapers
  • Sunken soft spot on the front of the head in babies (called the fontanel)
  • No tears when the child cries
  • Dry or sticky mucous membranes (the lining of the mouth or tongue)
  • Lethargy (less than normal activity)
  • Irritability (more crying, fussiness with inconsolability)

Dehydration in Children Causes

  • Dehydration is most often caused by fever, diarrhea, vomiting, and a decreased ability to drink or eat associated with a viral infection.
    • Common viral infections that cause vomiting or diarrhea include rotavirus, Norwalk virus, and adenovirus.
    • Sometimes sores in a child's mouth (caused by any several viruses) make it painful to eat or drink, which helps to cause or worsen dehydration.
  • More serious bacterial infections may make a child less likely to eat and may cause vomiting and diarrhea.
  • Parasitic infections by Giardia lamblia cause the condition known as giardiasis , which can lead to diarrhea and fluid loss.
  • Increased sweating from a very hot environment can cause dehydration.
  • Excessive urination can be caused by unrecognized or poorly treated diabetes mellitus (not taking insulin) or diabetes insipidus.
  • Conditions such as cystic fibrosis or celiac sprue do not allow food to be absorbed and can cause dehydration.

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.