Hypokalemia is a low serum potassium level below 3.5 mEq/L that can be life-threatening as it affects every body system. It is caused by total body potassium loss due to medications, aldosterone excess, vomiting, diarrhea, wounds, or renal disease. Symptoms include weakness, confusion, muscle paralysis, low blood pressure, heart problems, and digestive issues. Treatment involves monitoring the patient, replacing potassium orally or intravenously, and addressing the underlying cause while ensuring safety and a potassium-rich diet.