Which is a normal potassium range relevant to monitoring patients on Digoxin therapy?

• A. 2.0-4.0 mEq/L
• B. 3.5-5.1 mEq/L
• C. 4.5-6.0 mEq/L
• D. 3.0-5.0 mEq/L

Answer: (B)

Potassium level needs to stay in a normal range when a patient is on digoxin because potassium and digoxin interact at the same cellular site. If potassium is low, digoxin binds more readily, increasing the risk of digoxin toxicity and dangerous heart rhythms. If potassium is high, the drug’s effect can be diminished and another set of problems can arise. Keeping potassium around the middle of the normal range helps maintain a safe, effective level of digoxin.

The typical normal potassium range used for monitoring is about 3.5 to 5.0 mEq/L (often listed as 3.5–5.1 mEq/L on labs). Therefore, the option that falls within this normal range is the best choice. Ranges that drop below 3.5 suggest hypokalemia, increasing toxicity risk, while ranges above 5.0 suggest hyperkalemia, which is not ideal for safe monitoring.