5 Defects of Over Hydration. According to medical professionals drinking water is essential for the health of the body. It fulfills the fluid requirements so that our body performs its functions correctly. But what happen, when a person begin to drink too much water? Over hydration is also dangerous like dehydration. Drinking too much water reduces the level of sodium in our somatic cells. Some of the disadvantages of drinking too much water are as follows:- 1) Nausea and vomiting Drinking too much water causes nausea and vomiting. The symptoms of drinking too much water are the same as that of dehydration. Our kidneys have their own limitations. When someone drinks too much water the kidneys are unable to remove the extra water, resulting in unpleasant symptoms such as vomiting, nausea and diarrhea etc. 2) All day long headache Headaches are possibly due to over hydration or dehydration. Drinking too m...