Digoxin is a cardiac glycoside used for treating adults with mild to moderate congestive heart failure and for treating abnormally rapid atrial rhythms (atrial fibrillation, atrial flutter, atrial tachycardia). A therapeutic level must be maintained. Indications of toxicity include: Lack of appetite, nausea, vomiting, or diarrhea. Headache, confusion, anxiety, or hallucinations. Restlessness, weakness, or depression. Changes in vision such as blurred vision or seeing halos around bright objects.