Lack of drinking water, especially on a hot day can cause dehydration. Several things can cause dehydration, lack of body fluids that can be harmful. The following causes of dehydration according to the National Library of Medicine, United States:
•Diarrhea or vomiting
•Frequent urination, probably from uncontrolled diabetes or diuretic medication.
•Not eating due to nausea or no appetite.
•Was strep throat or sore blisters around the mouth.