Digitalis toxicity is a clinical emergency that can result in fatal arrhythmias. Arrhythmias from digitalis can vary greatly and include bradyarrhythmias, tachyarrhythmias, and atrioventricular block. Other symptoms of acute digitalis toxicity are hyperkalemia, nausea / vomiting, and mental status changes. Patients may complain of yellow vision (xanthopsia). Chronic toxicity may occur and presents with subtler clinical signs. Patients with chronic toxicity show neither markedly increased serum digoxin levels nor hyperkalemia. Digitalis toxicity is most commonly caused by intentional or unintentional overdose of digoxin, which is a medication used for atrial fibrillation and heart failure.

Digitalis toxicity rarely occurs from ingestion of plants such as foxglove or oleander. Digoxin Fab antibody fragment is available as an effective antidote to digitalis toxicity.