Short answer
What is the difference between orlistat, Xenical, and Alli?
They all contain the same active ingredient – orlistat. The difference is dose and how you get them. Alli is the 60 mg brand you can buy without a prescription. Xenical is the original brand-name prescription version at 120 mg. Generic orlistat 120 mg is the same prescription-strength dose without the Xenical branding, usually cheaper. They all work the same way: blocking roughly 30% of dietary fat from being absorbed.
Side by side
Orlistat, Xenical, and Alli: full comparison
| Feature | Alli | Xenical | Generic orlistat 120 mg |
|---|---|---|---|
| Active ingredient | Orlistat | Orlistat | Orlistat |
| Dose per capsule | 60 mg | 120 mg | 120 mg |
| Prescription required? | No – OTC pharmacy | Yes | Yes |
| Licensed BMI threshold | BMI ≥28 | BMI ≥30 (or ≥28 with co-morbidity) | BMI ≥30 (or ≥28 with co-morbidity) |
| Typical UK cost | ~£49 for 84 capsules (~4 weeks) | ~£43 for 84 capsules (~4 weeks) | ~£17 – £96/month depending on supplier |
| How to get it | Pharmacy or online (pharmacist check) | GP or online clinic | GP or online clinic |
| Mechanism | Lipase inhibition (~30% fat blocked) | Lipase inhibition (~30% fat blocked) | Lipase inhibition (~30% fat blocked) |
Which one suits you?
How to choose
Choose Alli if…
You do not want to involve a GP; your BMI is between 28 and 29; you want to try the lower dose first to assess tolerability; or you have a straightforward medical history with no regular medications that interact with orlistat.
Choose prescription orlistat 120 mg if…
Your BMI is 30 or above; you tried Alli and did not get sufficient results; you have a weight-related health condition such as type 2 diabetes; or you want the dose that was used in the main long-term clinical trials. Generic orlistat is usually the most cost-effective prescription option.
Choose Xenical (brand) if…
Your prescriber has specifically recommended the branded version, or you prefer a named brand. Clinically, generic orlistat 120 mg is equivalent to Xenical – the active ingredient, dose, and mechanism are identical. The main reason to choose the brand is personal preference or a specific clinical instruction.
Dosing reminder
How to take orlistat – for all versions
Where to buy
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FAQ
Common questions
Is generic orlistat as effective as Xenical?
Yes. Generic orlistat 120 mg contains the same active ingredient at the same dose as Xenical. They are bioequivalent, meaning the MHRA has confirmed they work the same way in the body. The only differences are brand name, packaging, and price.
Is Alli 60 mg worth it compared to the 120 mg prescription dose?
The 60 mg dose produces fewer side effects than 120 mg but also somewhat less weight loss on average. It may be a reasonable starting point if you are uncertain about tolerability, but if you need the full effect – particularly if your BMI is well above 30 – the prescription dose is more likely to produce clinically meaningful results.
Can I switch from Alli to prescription orlistat?
Yes. If you have tried Alli and want to move to 120 mg, speak to your GP or an online prescribing service. They will assess whether the higher dose is appropriate for you. There is no clinical reason you cannot switch – they are the same drug.
Related pages
Orlistat UK: full guide
How it works, cost, and where to buy. Read the guide.
Can you buy orlistat over the counter?
Yes – here is how the pharmacist check works. Read more.
Important
Information only
Tablet Compare is information only. Speak to a pharmacist or clinician before starting any weight-loss medication.