The most-common side effects of extended-release potassium chloride are nausea, vomiting, abdominal pain, diarrhea and excess gas, according to RxList. More severe gastrointestinal problems, such as ulceration, bleeding, obstruction and perforation have occurred as well. The most-serious adverse reaction, however, is hyperkalemia, or too much potassium in the blood. Very high potassium levels can lead to cardiac arrest and death.
Doctors prescribe potassium supplements to treat low levels of potassium in the blood, explains WebMD. While most people get enough potassium from the foods they eat, prolonged vomiting or diarrhea, hormonal abnormalities or treatment with diuretics, or "water pills," sometimes cause a person's potassium level to fall. Since potassium is important for proper functioning of the nerves, kidneys, muscles and heart, the patient usually takes a supplement until his levels return to normal.
To minimize the side effects of potassium chloride, take each dose with a meal and an 8-ounce glass of water, advises WebMD. Alternatively, break the tablet in half and take each half with 4 ounces of water, or dissolve the tablet in 4 ounces of water for about two minutes and drink the liquid. Rinse the glass with about 1 ounce of water, and then drink that as well. Never crush, suck on or chew potassium chloride extended-release tablets, because this may release all the medicine at one time, increasing the likelihood of side effects. Take no more than 20 milliequivalents of potassium chloride at one time.