Hypokalemia is a condition characterized by a potassium serum level below the normal range, typically less than 3.5 mmol/L. Potassium plays a critical role in cellular function, particularly in muscle and nerve excitability. Most potassium is intracellular, and the body carefully regulates serum potassium through renal excretion and cellular shifts. The causes of hypokalemia are diverse and can be grouped into transcellular shifts, renal losses, and extrarenal losses. Transcellular shifts, such as those triggered by insulin and beta-agonists, cause potassium to move from the blood into cells, lowering serum levels. Renal losses may result from diuretics, tubular disorders (like Bartter and Gitelman syndromes), or hyperaldosteronism, among others. Extrarenal losses include gastrointestinal causes such as vomiting, diarrhea, and malabsorption syndromes. Clinically, hypokalemia severity impacts presentation. Mild hypokalemia (3.0–3.4 mmol/L) may be asymptomatic, while severe hypokalemia (<2.5 mmol/L) can cause muscle paralysis, respiratory failure, and life-threatening arrhythmias such as torsades de pointes. ECG findings often reveal hypokalemia with flattened T waves, prominent U waves, and QT prolongation. Laboratory investigations for hypokalemia include serum electrolytes (K+, Na+, Mg2+, Ca2+), renal function tests, and arterial blood gases. Urinary potassium excretion ratios help differentiate renal from extrarenal potassium losses. Management focuses on safely correcting potassium deficiency by oral replacement for mild cases and intravenous supplementation for severe hypokalemia or when oral replacement is not feasible. Electrocardiographic monitoring is essential throughout treatment to avoid overcorrection and monitor for arrhythmias. Addressing underlying causes such as diuretic use, endocrine disorders, or gastrointestinal losses is crucial to prevent recurrence. Additional care includes correcting associated electrolyte imbalances such as hypomagnesemia, as magnesium deficiency can exacerbate hypokalemia and complicate treatment. This concise yet detailed overview supports medical and nursing students in understanding hypokalemia's pathophysiology, clinical features, and therapeutic approaches, making it a valuable resource for exam preparation and clinical practice.