A digoxin level is considered toxic if it exceeds which value?

• A. >0.2 ng/mL
• B. >10 ng/mL
• C. >5 ng/mL
• D. >2 ng/mL

Answer: (D)

Digoxin has a very narrow therapeutic window, so clinicians monitor its blood level carefully. The usual therapeutic range is about 0.5 to 2 ng/mL. When the level rises above 2 ng/mL, the risk of digoxin toxicity becomes significant, with symptoms and signs such as arrhythmias, GI upset, and vision changes. Among the given values, the threshold that commonly defines toxicity is just over 2 ng/mL. Levels well below that are generally considered subtherapeutic, and much higher levels indicate toxicity, with 5 or 10 ng/mL representing more severe toxicity, but the standard cut-off for recognizing potential toxicity is >2 ng/mL.