SN instructed patient and caregiver that potassium is available in foods such as asparagus, tomatoes and green leafy vegetables such as spinach. Some salt substitutes contain potassium. Avoid fruits like bananas and oranges if you are on a diabetic diet. If levels drop too low or spike too high, your heart function suffers, becoming slow or erratic, a condition known as arrhythmias. Because abnormal potassium levels greatly impact your heart function and can ultimately lead to a heart attack, it’s essential to follow your doctor’s advice carefully. Most common reasons for potassium loss is from vomiting, diarrhea, laxative use and diuretic use.