Water is a critical element of the body, and adequate hydration is a must to allow the body to function. Up to 75% of the body's weight is made up of water. Most of the water is found within the cells of the body (intracellular space). The rest is found in what is referred to as the extracellular space, which consists of the blood vessels (intravascular space) and the spaces between cells (interstitial space).

Total body water = intracellular space + intravascular space + interstitial space

Dehydration occurs when the amount of water leaving the body is greater than the amount being taken in. The body is very dynamic and always changing. This is especially true with water in the body. We lose water routinely when we:

• breathe and humidified air leaves the body
• sweat to cool the body
• urinate or have a bowel movement to rid the body of waste products.

If intravascular (within the blood vessels) water is lost, the body can compensate somewhat by shifting water from within the cells into the blood vessels, but this is a very short-term solution. The body lives within a very narrow range of normal parameters, and signs and symptoms of dehydration will occur quickly if the water is not replenished.

The body is able to monitor the amount of fluid it needs to function. The thirst mechanism signals the body to drink water when the body is dry. As well, hormones like anti-diuretic hormone (ADH) work with the kidney to limit the amount of water lost in the urine when the body needs to conserve water.

This answer should not be considered medical advice...This answer should not be considered medical advice and should not take the place of a doctor’s visit. Please see the bottom of the page for more information or visit our Terms and Conditions.