Digoxin: what it treats, how to take it, side effects
Last updated September 3, 2026.
Digoxin is a cardiac glycoside - one of the oldest heart medicines in use - that helps the heart beat stronger and steadier. You may know it as Lanoxin. It works within a narrow window: the label notes toxic blood levels sit only slightly above therapeutic ones, which is why this drug comes with pulse checks and blood tests.
What does it treat?
Heart failure and abnormal heart rhythms (arrhythmias). It helps the heart work better and helps control your heart rate.
How do you take it?
Usually once a day, same time every day, exactly as directed. The same-brand rule is real: different brands of digoxin contain different amounts of active drug, so always take the same brand - if your pharmacy switches it, your dose may need to change. The pediatric elixir comes with a specially marked dropper; ask your pharmacist to show you how to use it. Monitoring is part of the medication: expect periodic EKGs and blood tests, and your doctor may teach you to check your pulse - if it runs faster or slower than it should, call. Your doctor may also recommend a low-sodium diet and a potassium supplement; follow those directions closely. Never stop without your doctor. Missed dose: take it when you remember unless the next one is close; never double up.
Side effects to know
- Common: dizziness or lightheadedness, drowsiness, vision changes including blurred or yellow-tinted vision, rash, and irregular heartbeat. It can make you drowsy, and alcohol adds to that.
- Serious - call your doctor immediately: upset stomach, vomiting, diarrhea, loss of appetite, swelling of the feet or hands, unusual weight gain, and difficulty breathing. The stomach cluster plus vision changes and a slow or irregular pulse is the classic digoxin-toxicity picture - treat it as urgent, not routine.
Who should not take it?
If you are 65 or older, MedlinePlus says older adults should usually receive low doses - higher doses can cause serious side effects. Flag thyroid problems, heart rhythm problems, cancer, and kidney disease - kidney function drives how fast the drug clears, and accumulation is the toxicity risk. The interaction list is long and specific: antacids, the acid reducers esomeprazole, lansoprazole, and omeprazole, St. John's wort, neomycin, activated charcoal, and calcium supplements all interact - do not start any of them without discussing with your healthcare provider. If you become pregnant, call your doctor.
When is it an emergency?
Fainting, difficulty breathing, or a heartbeat that is very slow, very fast, or erratic is a 911 call. Vomiting with yellow or blurred vision and a slow pulse means immediate care - that is the toxicity pattern. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Why does my pharmacist insist I stay on the same brand of digoxin?
Because brands are not interchangeable here. MedlinePlus says it directly: different brands of digoxin have different amounts of active drug, and switching brands can mean your dose needs to change. If your tablets ever look different, ask before taking them - that one question prevents a real dosing error.
Why does digoxin need blood tests and pulse checks?
The safety window is narrow. The label states that toxic digoxin levels are only slightly higher than therapeutic ones - the difference between working and poisoning is small, and it moves with kidney function, weight, age, and other drugs. The blood tests measure where you are in the window; the daily pulse is your at-home early warning. Faster or slower than it should be means calling your doctor.
What does digoxin toxicity feel like?
Stomach first, then eyes and heart. MedlinePlus's serious list reads like the toxicity textbook: upset stomach, vomiting, diarrhea, loss of appetite, plus the vision changes - blurred or yellow-tinted - and an irregular heartbeat. Any combination of those on digoxin is a same-day call, not a watch-and-wait.
Can I take antacids or calcium with digoxin?
Not without asking. MedlinePlus names antacids, calcium supplements, the acid reducers esomeprazole, lansoprazole, and omeprazole, St. John's wort, neomycin, and activated charcoal as interacting products - each can shift how much digoxin your body absorbs or holds. Bring the full list of everything you take to your doctor or pharmacist before adding anything.
Why did my doctor mention potassium with digoxin?
Because low potassium raises the toxicity risk. MedlinePlus says your doctor may recommend a low-sodium diet and a potassium supplement with digoxin - the drug's behavior at heart cells depends on potassium levels. If you are prescribed the supplement, take it as directed, and ask before using salt substitutes or changing your diet on your own.
What happens if I miss a dose of digoxin?
Take it as soon as you remember, unless it is almost time for the next one - then skip it and never double up. Doubling is the real danger on a drug with this narrow a window. One missed dose is minor; a double dose can push levels toward toxic.