Diuretic abuse, as well as causing dehydration, can lead to fluid retention and weight gain. In an attempt to adjust to the diuretic effects, the body will retain water. Abusing this type of medication can also lead to dizzy spells and fainting. Diuretics are commonly used to lower blood pressure. So, in a person with normal blood pressure, the diuretic effects can cause hypotension. Diuretics are not meant to be weight loss tools and can cause serious side effects including, but not limited to, increased uric acid levels and hypokalemia.