According to MedicineNet, dehydration or lack of enough water in the body happens because there is too much loss of water, not enough water taken in, or most commonly, a combination of the two. Some of the causes of dehydration are:
Diarrhea is the most common reason for an individual to lose excess amounts of water. A significant amount of water can be lost with each bowel movement. Globally, more than 4 million children die every year because of dehydration from diarrhea.
Vomiting can also be a trigger of water loss. Not only can a person lose fluid in the vomitus, but it may be tough to replace water by drinking due to that same nausea and vomiting.
The body can lose high amounts of water in the form of sweat when it tries to cool itself. Whether the body temperature is hot because of working or exercising in a hot environment or because a fever is present as a result of an infection; the body uses water in the form of sweat to cool itself. Depending upon weather conditions, a brisk walk may generate up to 16 ounces of sweat in one hour to let the body cool, and that water requires to be replaced by the thirst mechanism indicating the person needs to drink fluids.
In people with diabetes, high blood sugar levels make sugar spill into the urine and water then follows, which may result in significant dehydration. For this reason, constant urination and high level of thirst are among the early symptoms of diabetes.
The skin serves as a protective barrier for the body and is also responsible for the control of fluid loss. Burn victims get dehydrated because the damaged skin is unable to prevent fluid from seeping out of the body. Other inflammatory diseases of the skin like toxic epidermal necrolysis, also may be linked with significant fluid loss.
6. Inability to drink fluids
The inability to consume water adequately is the other potential cause of dehydration, whether it is the lack of availability of water, severe nausea with or without vomiting, or the lack of strength to drink. This coupled with routine or extraordinary water losses can spike the degree of dehydration.