Psyllium Husk and medications.
Psyllium Husk is in the Distil supplement database, evidence Grade A. The page below lists every medication we have explicitly assessed it against.
Psyllium husk is a soluble fibre that forms a gel in the gut, and that gel does most of the work. The evidence is Grade A for lowering LDL cholesterol and blood pressure and for improving bowel transit, with useful effects on blood glucose and satiety too. Zhu 2024 and earlier meta-analyses back the cholesterol and glycaemic findings. Doses are 5 to 10g twice daily, and there is one rule that is not optional: take it with at least 240ml of water, because without enough fluid it can cause bowel obstruction. The interaction point is simple but broad. Psyllium blunts the absorption of medicines, so it needs a two-hour gap from all medications, every time. On the positive side it acts as a prebiotic and feeds probiotic bacteria. Expect some bloating and gas in the first week as your gut adjusts. Plenty of water, a two-hour spacing from drugs, and psyllium is one of the better-evidenced fibres available.
Below are the 3 documented pairs we have explicitly assessed for Psyllium Husk: 2 amber and 1 green. The pairs cluster around 1 mechanism: Absorption interference. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not listed here is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by medication, and the missing-item form at the bottom of the page routes any uncatalogued medication 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.
Psyllium may reduce how much lithium you absorb if you take them together, which could lower your lithium level below the range that keeps you well. Take your psyllium at least a few hours apart from your lithium, and keep to your scheduled lithium blood tests so any drop is picked up.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Psyllium taken at the same time as levothyroxine causes only a small reduction in how much levothyroxine you absorb, and a direct study found the difference was not large enough to matter. Levothyroxine is best taken on an empty stomach anyway, so keeping your psyllium to a different part of the day is sensible rather than essential.
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. Use the checker below to surface any medication, and submit a missing item if you take something we have not catalogued.
For adults over 18.
This tool gives evidence-graded information, not medical advice. Always discuss changes with your GP, pharmacist, or specialist before making them, especially if you take any medication, are pregnant, breastfeeding, or have a serious health condition.
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 methodologySomething missing?
If a supplement or medication you take isn't in our autocomplete, tell us. We go through what people flag every week and add what's missing.