Supplements and Digoxin.
Digoxin, sold under the brand name Lanoxin, is a cardiac glycoside: it increases cardiac contractility and slows AV conduction. The therapeutic window is narrow.
Digoxin is a cardiac glycoside. In current UK clinical practice that means digoxin. The therapeutic window is narrow. Trough levels are monitored because the gap between therapeutic and toxic concentrations is small. Digoxin clearance is renal, and any decline in renal function (acute kidney injury, dehydration, CKD progression) pushes plasma levels up. The supplement surface includes anything that affects renal handling, anything that depletes potassium (since hypokalaemia worsens digoxin toxicity), and anything that inhibits P-glycoprotein. St John's Wort induces P-gp and lowers digoxin levels. Certain supplements at high doses inhibit P-gp and raise them. Liquorice in real or DGL form at high intake is the textbook concerning combination, because it both depletes potassium and acts on cardiac conduction itself. Digoxin toxicity presents with nausea, visual changes (a yellow or green tinge), and arrhythmia.
Below are the 11 documented pairs we have explicitly assessed against Digoxin in the Distil database: 11 amber. The pairs cluster around 6 mechanisms: Absorption interference, Mineral chelation (absorption), Digoxin assay interference, Digoxin-potassium balance (keep in range), Hypercalcaemia risk, and P-glycoprotein interaction. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not on this list is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by supplement, and the missing-item form at the bottom of the page routes any uncatalogued supplement into our next curation pass.
Documented interactions
Absorption interference
Psyllium taken at the same moment as digoxin may slightly reduce how much digoxin you absorb, though a controlled study found no effect on steady digoxin levels over time. As a precaution with a narrow-margin drug, take psyllium a couple of hours apart from your digoxin.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Mineral chelation (absorption)
There are two things to know here, and on balance magnesium is more helpful than harmful. Taking magnesium at the same time as digoxin can slightly reduce how much digoxin you absorb, so it is sensible to separate them by about two hours. At the same time, a low magnesium level makes digoxin more likely to cause dangerous heart rhythms, so keeping your magnesium in the normal range is protective. Because digoxin has a narrow safe range, tell whoever prescribes it that you take magnesium.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
There are two things to know here, and on balance magnesium is more helpful than harmful. Taking magnesium at the same time as digoxin can slightly reduce how much digoxin you absorb, so it is sensible to separate them by about two hours. At the same time, a low magnesium level makes digoxin more likely to cause dangerous heart rhythms, so keeping your magnesium in the normal range is protective. Because digoxin has a narrow safe range, tell whoever prescribes it that you take magnesium.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
There are two things to know here, and on balance magnesium is more helpful than harmful. Taking magnesium at the same time as digoxin can slightly reduce how much digoxin you absorb, so it is sensible to separate them by about two hours. At the same time, a low magnesium level makes digoxin more likely to cause dangerous heart rhythms, so keeping your magnesium in the normal range is protective. Magnesium L-threonate is still elemental magnesium, so both points apply. Because digoxin has a narrow safe range, tell whoever prescribes it that you take magnesium.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Digoxin assay interference
Siberian ginseng can make a digoxin blood test read higher (or lower) than your true level, depending on which test the lab uses. There is one older case where digoxin readings rose while taking it and fell each time it was stopped. Because digoxin has a narrow safe range, tell your GP or cardiology team if you take Siberian ginseng, and mention it before any digoxin level is checked.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Digoxin-potassium balance (keep in range)
Potassium and digoxin are closely linked. Keeping your potassium in the normal range is actually important on digoxin: when potassium runs low, digoxin becomes more toxic and can affect the heart rhythm. So a potassium supplement is not something to simply avoid. The catch is balance. Too much potassium can reduce how well digoxin works and, if it climbs too high, add to the risk of a slow or irregular heartbeat. Do not start a potassium supplement on your own while taking digoxin. Let your doctor decide whether you need one and have your potassium checked, especially if your kidneys are not working at full capacity or you take other medicines that raise potassium.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Hypercalcaemia risk
A calcium supplement can raise blood calcium, and a high calcium level makes the heart more sensitive to digoxin, which already has a narrow safe range. Modest calcium doses with normal blood calcium are not expected to be a problem, but larger calcium intake, or calcium taken with high-dose vitamin D, is worth discussing with your prescriber so your calcium and digoxin can be kept in check.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
High-dose vitamin D can raise blood calcium, and a high calcium level makes the heart more sensitive to digoxin, which already has a narrow safe range. Standard replacement doses of vitamin D with normal calcium are not expected to be a problem, but high-dose vitamin D, or vitamin D plus calcium supplements, is worth discussing with your prescriber so your calcium and digoxin can be kept in check.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
P-glycoprotein interaction
Berberine may raise digoxin blood levels by slowing how the gut pumps it back out. Digoxin has a narrow safe range, so if you take both, watch for nausea, visual changes or an irregular pulse and ask your GP whether a digoxin level check is worthwhile.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Quercetin may slow how the body clears digoxin by blocking a transporter pump (P-glycoprotein), which can push digoxin levels higher. Digoxin has a narrow safe range, so if you take it, speak to your GP before adding quercetin and do not start a high-dose supplement without that conversation.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
St John's Wort tends to reduce how much digoxin reaches your bloodstream, which may make it less effective at the prescribed dose. Because digoxin has a narrow safe range, do not start or stop St John's Wort while on digoxin without telling whoever prescribes it, so your dose and levels can be checked.
What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope (food-supplement interactions only; for drug-drug interactions, the BNF is authoritative). Use the checker below to surface any supplement, and submit a missing item if you take something we have not catalogued.
How we grade severity, choose what's in scope, and what we exclude.
Every call on this page is reasoned. We publish the full rubric for severity tiers, the medication inclusion logic, the evidence grades we accept, and what we deliberately leave out. About three thousand words. Worth reading once if you use this tool more than occasionally.
Read the full methodologyWant this checked across everything you take?
This page checks the pairs you enter. The personalised Distil report goes further:
- the same graded, cited interaction check across your whole stack, not just the pairs you thought to type in
- where your current routine may be leaving you short of your goals
- the evidence-backed compounds worth adding, and the ones worth dropping
It's a paid report: £79, or £49 for the first 25 customers. The interactions check is one section of it, and you can read a real one in full before you buy.
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