Medication · other drugs used in the treatment of obesity

Supplements and Orlistat.

Every documented pair, every citation. Below: 1 documented pair grouped by mechanism.

Orlistat, sold under the brand names Xenical, Alli, is classified under "drugs used in the treatment of obesity" in the BNF.

Orlistat (UK brand names Xenical, Alli) sits at NHSBSA prescribing rank 194 in the 2024/25 PCA statistics. The BNF classifies it under "drugs used in the treatment of obesity". This means it sits outside the high-volume therapeutic classes (statins, PPIs, ACE inhibitors, SSRIs) where supplement-interaction surfaces are densely studied, and the published evidence base for specific supplement pairs is correspondingly thinner. Where interactions are documented in the Distil database, they are listed below with their clinical-reference citation; where pairs have not been explicitly assessed, the missing-item form at the bottom of the page routes them into our next curation pass. Anyone combining Orlistat with a regular supplement stack benefits from explicit GP or pharmacist awareness rather than assuming no interaction exists by default.

Below are the 1 documented pair we have explicitly assessed against Orlistat in the Distil database: 1 amber. 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 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

Amber Vitamin D3

Orlistat works by blocking the gut from absorbing some dietary fat, and because vitamin D is fat-soluble it gets absorbed less well too. This may lower your vitamin D level over time, even if you take a supplement at the same time of day. The usual advice is to separate them: take your vitamin D (or a fat-soluble multivitamin) at bedtime, at least 2 hours away from any orlistat dose, and your prescriber may check your vitamin D level.

PMID 12126214 · PMID 24915331 · BNF: Orlistat

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.

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For adults over 18. This tool gives evidence-graded information, not medical advice. Always discuss changes with your GP, especially if you take any medication, are pregnant, breastfeeding, or have a serious health condition.

Your supplements

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Your medications

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Pick any that apply. We adjust the findings where context changes the answer.

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How we decide

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 methodology

Your whole stack

Want 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.

See a real sample report

Something 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.

Thanks, that's logged. We go through flagged items every week.

Distil's interactions database is reviewed and updated every quarter. We grade evidence transparently and publish our methodology, including every database change, at /about/methodology. This tool is information, not a substitute for clinical judgement. If you take medication and supplements together, your GP or pharmacist can review your full regimen against your medical history. If you want a full personalised stack reasoned against this same database, the Distil report is the next step up.