What are the signs and symptoms of hypokalemia?

Hypokalemia, defined as serum potassium below 3.5 milliequivalents per liter, causes muscle weakness, leg cramps, fatigue, constipation and decreased bowel sounds from smooth muscle weakness, flattened T waves and the appearance of U waves on electrocardiogram, and cardiac arrhythmias. Severe hypokalemia can cause respiratory muscle weakness and cardiac arrest. Common causes include loop and thiazide diuretics, vomiting, nasogastric suctioning, and diarrhea. Hypokalemia also increases sensitivity to digoxin toxicity. Treatment includes oral or intravenous potassium replacement.