Which electrolyte abnormalities are characteristic of digoxin toxicity?

• A. I only
• B. II only
• C. I, II
• D. II, III

Answer: (C)

Digoxin toxicity disrupts ion balance by inhibiting the Na+/K+-ATPase pump in heart cells. This causes potassium to shift out of cells, raising extracellular potassium levels, so hyperkalemia is a characteristic lab finding of digoxin overdose. Magnesium also plays a role: low magnesium (hypomagnesemia) can predispose to toxicity and worsen its effects because Mg helps modulate the pump and cellular excitability; when Mg is low, digoxin binds more readily and toxicity increases. So the pattern you’re looking for involves elevated potassium along with low magnesium.