Symptoms of Potassium Deficiency. Found out, the VERY hard way, that RSD causes potassium deficiency due to excessive sweating (in my case, at night, as we sleep on the 2nd floor & heat rises + we have a heated water bed). Low K can cause black outs, seizures & heart attacks. VERY IMPORTANT to get your potassium levels checked by your Dr. I have to take a daily Rx due to the fact that OTC supplements are no where near enough.