Dehydration is a serious medical condition. MayoClinic.com says, "Dehydration occurs when you 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 replenish lost fluids, you may suffer serious consequences." Dehydration may be caused by several different things, including severe diarrhea, vomiting or even forgetting to intake fluids in intensely hot weather. Knowing the signs and symptoms of dehydration is essential to avoiding it.