What happens when I am dehydrated?

dried up soil photo
Photo by Dan Gold on Unsplash
Play Video


The human body is made up of roughly 50 -70% water depending on age and gender. It is stored in different percentages throughout the body.

What is this?

TL;DR (or tl;dr) stands for "too long; didn't read" - it's our way of summing up a topic

Table of Contents

The human body is made up of roughly 50 -70% water depending on age and gender.  It is stored in different percentages throughout the body.

Body partWater percentage
brain and heart73%
muscles and kidneys79%

When does dehydration occur?

When you use or lose more fluid than you take in, and your body doesn’t have enough water and other fluids to carry out its normal functions. If you don’t replace lost fluids, you will get dehydrated.

Dehydration is especially dangerous for young children and older adults.

Common causes of hydration

Young children:

  • Severe diarrhea and vomiting

Older adults:

  • Naturally have a lower volume of water in their bodies and may have conditions or take medications that increase the risk of dehydration.
  • Meaning that even minor illnesses, such as infections affecting the lungs or bladder, can result in dehydration

Dehydration also can occur in any age group if you don’t drink enough water during hot weather, especially if you are exercising vigorously.

Mitigating dehydration

You can usually reverse mild to moderate dehydration by drinking more fluids, but severe dehydration needs immediate medical treatment.

Thirst isn’t always a reliable early indicator of the body’s need for water. Many people, particularly older adults, don’t feel thirsty until they’re already dehydrated. That’s why it’s important to increase water intake during hot weather or when you’re ill.

Signs and symptoms may differ by age:

Infant or young child

  • Dry mouth and tongue
  • No tears when crying
  • No wet diapers for three hours
  • Sunken eyes, cheeks
  • Sunken soft spot on top of skull
  • Listlessness or irritability


  • Extreme thirst
  • Less frequent urination
  • Dark-colored urine
  • Fatigue
  • Dizziness
  • Confusion

Find this topic useful? Share it with the world!

Related Topics

Ask the Experts

Can’t find the answer to your wellness question?

We’d love to hear from you.