Quick facts
Low potassium raises the risk of digoxin toxicity
- Hypokalemia increases digoxin's effect and can lead to digoxin toxicity, so potassium is watched closely in patients taking digoxin. Report a result below 3.5 mEq/L promptly.[4]
- Loop diuretics such as furosemide often deplete potassium, so the potassium result is reviewed before each dose. Giving one when potassium is already low worsens the hypokalemia, and that can trigger a life-threatening arrhythmia.[4]
High potassium: check the kidneys, the drug list and the blood draw
- Kidney failure, metabolic acidosis, ACE inhibitors, potassium supplements and potassium-sparing diuretics such as spironolactone can all raise potassium.[2][4]
- Signs of hyperkalemia are mostly cardiac. ECG changes can progress to dysrhythmias and cardiac arrest as the level climbs, and irritability, cramping and diarrhea can also appear.[2]
- Clenching and relaxing the fist over and over just before or during the draw can briefly raise the potassium result and give an incorrect reading.[5]
IV potassium is never given as a push
- Potassium is given by mouth or mixed into IV fluid as an infusion, never by IV push, because a push can stop the heart. IV potassium given too fast can also cause cardiac arrest.[2]
Potassium sits in the Basic metabolic panel flashcard deck with sodium, chloride, and the rest of the panel. Find the deck in the free app preview.
Open the free app previewHow it shows up on nursing exams
- In a priority question, rank a low potassium in a patient taking digoxin or a loop diuretic above any in-range value, because hypokalemia adds to the risk of digoxin toxicity and arrhythmia.[4]
- Read the number before the drug name. ACE inhibitors and potassium-sparing diuretics can raise potassium, but a result between 3.5 and 5.1 mEq/L is still in range.[1][2]
Practice question
A nurse on a cardiac step-down unit reviews morning serum potassium results for four adult patients. The laboratory reference range is 3.5 to 5.1 mEq/L. Which patient's result should the nurse report to the health care provider first?
- A. Heart failure, taking spironolactone: potassium 4.9 mEq/L
- B. Atrial fibrillation, taking digoxin: potassium 3.1 mEq/L
- C. Heart failure, taking furosemide: potassium 3.6 mEq/L
- D. Hypertension, taking lisinopril: potassium 5.0 mEq/L
Show the answer and why
Correct answer: B. Atrial fibrillation, taking digoxin: potassium 3.1 mEq/L
- A. Incorrect. 4.9 mEq/L is inside the 3.5 to 5.1 range. Spironolactone, a potassium-sparing diuretic, can cause hyperkalemia, so potassium stays on the watch list, but this value is not abnormal.
- B. Correct. 3.1 mEq/L is below 3.5. Hypokalemia increases digoxin's effect and can lead to digoxin toxicity, and a result below 3.5 in a patient taking digoxin is reported promptly. This is the result to report first.
- C. Incorrect. 3.6 mEq/L is low-normal but inside the range. Furosemide often depletes potassium, so the result is reviewed before each dose, but it does not outrank a value that is already below 3.5.
- D. Incorrect. 5.0 mEq/L is high-normal but inside the range. Lisinopril is an ACE inhibitor, and its label calls for periodic potassium checks because these drugs can cause hyperkalemia. It is not the first report.
Sources for this question: [1][4][6]
Memory hook: Potassium is a heart lab: check it before digoxin or furosemide, and never give it IV push.