What happens when you take digoxin with licorice?
Digoxin is a narrow-therapeutic-index cardiac glycoside used to slow heart rate in atrial fibrillation and provide modest inotropic support in heart failure. Its effect depends heavily on potassium: when serum potassium drops, digoxin binds more tightly to the cardiac Na+/K+ ATPase, and toxic effects can occur even at otherwise therapeutic blood levels. Licorice can lower potassium, and that is where the two collide.
- Glycyrrhizin is converted to its active metabolite. Licorice (Glycyrrhiza glabra) contains glycyrrhizin, which the body converts to glycyrrhetinic acid.
- A kidney enzyme is blocked. Glycyrrhetinic acid inhibits 11-beta-hydroxysteroid dehydrogenase type 2 (11-beta-HSD2), the enzyme that normally keeps cortisol from acting on the mineralocorticoid receptor.
- Pseudoaldosteronism develops. With the enzyme blocked, cortisol activates the mineralocorticoid receptor, causing sodium and water retention, higher blood pressure, and urinary potassium loss. This is called apparent mineralocorticoid excess.
- Potassium falls. With regular licorice intake, potassium can drop enough to be clinically significant.
- Digoxin is sensitized. Falling potassium increases digoxin's binding affinity for its cardiac target, so toxic electrophysiologic effects can occur even when serum digoxin levels appear therapeutic.
The key point is that this is not a direct pharmacokinetic interaction with digoxin. It is the licorice-induced drop in potassium that creates the danger.
Why is this important?
Digoxin toxicity can be serious. Early symptoms include nausea, vomiting, abdominal pain, fatigue, visual disturbances (classically yellow-green halos around lights), and confusion. Cardiac manifestations can include atrial tachycardia with block, ventricular bigeminy, AV block, and in severe cases ventricular tachycardia or fibrillation. Significant poisoning requires hospital care, electrolyte correction, and occasionally digoxin-specific antibody fragments.
The risk is higher in older adults, in people with kidney impairment (which slows digoxin clearance), and in those also taking diuretics that further lower potassium — a common situation in heart failure. A single licorice exposure rarely causes a problem; it is regular, day-after-day consumption over weeks that tends to produce meaningful hypokalemia.
This interaction is documented rather than theoretical. A review of licorice toxicity by Omar and colleagues describes a patient who developed digoxin toxicity attributed to licorice-induced hypokalemia, and the U.S. FDA has issued a consumer advisory warning that eating black licorice regularly can lower potassium and lead to heart rhythm problems, particularly in older adults.
What should you do?
The practical rule is to avoid glycyrrhizin sources while taking digoxin, and to involve your doctor or pharmacist if you have already been using them.
- Before changing anything: If you take digoxin and have been consuming licorice regularly, tell your prescriber. They can check serum potassium, magnesium, and digoxin levels and review your ECG. Do not stop digoxin on your own.
- Every day on digoxin: Skip black licorice candy, licorice-flavored herbal teas, and licorice root capsules. Before buying lozenges, herbal blends, or traditional formulas, read labels for glycyrrhizin, licorice root, or gan cao — including products labeled DGL, which can occasionally contain residual glycyrrhizin.
- After any change or if symptoms appear: Seek prompt evaluation if you develop nausea, vomiting, palpitations, visual changes, or unusual fatigue. If you and your prescriber decide to stop licorice, potassium typically recovers, but levels and digoxin response should still be rechecked.
Red licorice does not contain real licorice extract and is not a concern. Deglycyrrhizinated licorice (DGL), used for heartburn, has had the glycyrrhizin removed and is generally lower-risk — but verify the label.
Which specific products are affected?
Glycyrrhizin-containing products to be cautious with include black licorice candy (such as Panda or Australian-style black licorice), licorice root extract supplements, licorice-flavored herbal teas, herbal blends marketed for adrenal support or low blood pressure, traditional Chinese formulas containing gan cao, certain throat and cough lozenges, and some anise- and licorice-flavored liqueurs.
On the medication side, the concern applies to all digoxin products — Lanoxin tablets, generic digoxin tablets, and pediatric oral solution — because the interaction depends on the resulting low potassium, not on the formulation. Other digitalis-like medications such as digitoxin (where available) raise the same concern. Some products labeled DGL still contain residual glycyrrhizin, so labels are worth reading carefully.
The science behind it
The mechanism is well characterized. Glycyrrhetinic acid, the active metabolite of glycyrrhizin, inhibits 11-beta-HSD2, producing apparent mineralocorticoid excess with sodium retention, hypertension, and hypokalemia. Omar and colleagues, in a review of licorice toxicity with case summaries, describe this pathway and report a patient who developed digoxin toxicity in the setting of licorice-induced hypokalemia, illustrating the clinical link between the two (Ther Adv Endocrinol Metab. 2012; PMID 23185686).
From a regulatory standpoint, the U.S. FDA's consumer advisory on black licorice warns that regular consumption can lower potassium and lead to abnormal heart rhythms and other effects, with older adults at greater risk. Together, the mechanistic review and the regulatory advisory support both the direction of the interaction and its potential seriousness, while the strongest evidence remains case-level rather than from controlled trials.
Frequently Asked Questions
Is red licorice a problem with digoxin?
No. Red licorice and most "licorice" candies in some regions contain no real licorice extract and therefore no glycyrrhizin. The concern is specifically black licorice and genuine licorice root products.
Is one piece of licorice dangerous?
A single small exposure is unlikely to cause trouble. The risk comes from regular consumption over days to weeks, which is what tends to lower potassium enough to matter.
Is DGL (deglycyrrhizinated licorice) safe with digoxin?
DGL has had the glycyrrhizin removed and is generally considered lower-risk. However, some products labeled DGL can still contain residual glycyrrhizin, so check the label and ask your pharmacist if unsure.
What symptoms should make me seek help?
Nausea, vomiting, unusual fatigue, palpitations or an irregular heartbeat, and visual changes such as yellow-green halos around lights all warrant prompt medical evaluation while on digoxin.
Should I stop my digoxin if I have been eating licorice?
No. Do not stop digoxin on your own. Tell your prescriber so they can check your potassium and digoxin levels and advise you. Stopping licorice is the change to make, not stopping your heart medication.
Are diuretics part of the picture?
Yes. Many people on digoxin also take diuretics, which themselves lower potassium. Adding licorice on top compounds the potassium loss, making this combination especially worth avoiding.
Key takeaways
- Licorice and digoxin is a high-severity interaction driven by glycyrrhizin lowering potassium, which sensitizes the heart to digoxin.
- The danger comes from regular licorice consumption over time, not a single exposure.
- Avoid black licorice candy, licorice root supplements, and other glycyrrhizin-containing products while taking digoxin.
- Red licorice is not a concern; DGL is generally lower-risk but read labels.
- Diuretics plus licorice plus digoxin is a particularly high-risk combination.
- If you have been using licorice, do not stop digoxin on your own — ask your doctor or pharmacist to check potassium and digoxin levels.