Orlistat, Xenical and Alli: a complete guide for UK weight loss

If you’ve been searching for orlistat weight loss pills, Xenical tablets, Alli diet pills or over the counter weight loss pills, you’re really looking at different versions of the same active ingredient: orlistat.

In the UK, orlistat medication is one of the few fat-blocking weight loss pills that’s properly licensed and widely used – both on NHS prescription and over the counter (OTC) at pharmacies.

This guide covers:

• How orlistat tablets/pills actually work

• The difference between Xenical 120 mg (prescription) and Alli 60 mg (OTC)

• Who orlistat is for (NHS vs private BMI rules)

• Typical results and what orlistat weight loss reviews tend to say

• Common side-effects (including the infamous oily stools) and how diet changes reduce them

• How to buy orlistat / buy Xenical online safely in the UK

What is orlistat – and how does it work for weight loss?

Orlistat is a fat-blocking medicine. It doesn’t work by suppressing your appetite or affecting your brain. Instead, it acts inside your gut.

Orlistat mechanism in simple terms

When you eat, enzymes called pancreatic and gastric lipases break down the fat in your food so it can be absorbed. Orlistat blocks these enzymes, so around 25–30% of the fat you eat isn’t absorbed and passes out in your stool instead.

That means:

• You actually absorb fewer calories from each meal

• You see the most benefit if you stick to a reduced-calorie, lower-fat diet – otherwise side-effects can be rough

Importantly, orlistat medication works only on fat in the gut. It doesn’t:

• Reduce sugar absorption

• Change your metabolism

• Act as a stimulant or appetite suppressant

This makes it very different from older “diet pills” and from modern GLP-1 injections like Wegovy or Saxenda.

Orlistat, Xenical and Alli: what’s the difference?

All three share the same active ingredient: orlistat. The differences are dose, licensing and how you access them.

Xenical orlistat 120 mg – prescription only

Xenical® 120 mg capsules are a prescription-only medicine (POM).

• Active ingredient: orlistat 120 mg per capsule

• Typical dose: one 120 mg capsule with each main meal (up to three times a day) that contains fat; skip if the meal is fat-free or missed.

• Indication: adults with BMI ≥ 30 kg/m², or BMI ≥ 28 kg/m² with risk factors (e.g. type 2 diabetes, hypertension, high cholesterol), used alongside a modestly reduced-calorie diet.

Xenical is what your GP or weight-management clinic would use when they prescribe orlistat tablets from a doctor on the NHS or privately.

Alli orlistat 60 mg – over the counter weight loss pill

Alli® 60 mg capsules are the lower-dose OTC version of orlistat.

• Active ingredient: orlistat 60 mg per capsule

• Dose: one 60 mg capsule with each fat-containing meal, up to three times daily

• Indication: adults 18+ with BMI ≥ 28 kg/m² who are following a reduced-calorie, lower-fat diet

You can buy Alli medication directly from a pharmacist (no prescription), but they should still check:

• Your BMI

• Other health conditions / meds

• That you understand the diet changes and side-effects

So:

• Xenical 120 mg = higher dose, prescription only

• Alli 60 mg = lower dose, pharmacy / OTC

Generic orlistat 120 mg capsules are also available as prescription-only orlistat pills, equivalent to Xenical at a lower price.

Who are orlistat tablets for in the UK? (NHS vs private)

NHS prescription orlistat

NHS guidance and local formularies usually allow orlistat prescription when:

• BMI is ≥ 30 kg/m², or

• BMI is ≥ 28 kg/m² with weight-related risk factors (e.g. type 2 diabetes, hypertension, dyslipidaemia, sleep apnoea)

And typically only if:

• You’ve already tried diet and lifestyle changes, and

• You’ve achieved at least a small initial weight loss (e.g. ≥2.5 kg over 4 weeks), and

• You’re reviewed at 3 months and only continue if you’ve lost ≥5% of starting weight

So orlistat is usually part of a structured weight-management plan, not a first-line option for mild overweight.

Orlistat over the counter (Alli)

For Alli orlistat 60 mg, the marketing authorisation is:

• Adults ≥18 years

• BMI ≥ 28 kg/m²

• Using a reduced-calorie, lower-fat diet

Even though Alli is an OTC orlistat weight loss pill, pharmacists are advised to screen for:

• Pregnancy / breastfeeding

• Chronic malabsorption or cholestasis

• Significant kidney disease (due to rare risk of kidney stones)

• Interactions (e.g. certain anticoagulants, levothyroxine, antiepileptics)

How much weight can you lose with orlistat?

Clinical trials and reviews suggest that, compared with lifestyle changes alone, orlistat medication can produce modest but clinically meaningful extra weight loss:

• One review found an average weight loss of ~5–6 kg over 6 months with orlistat vs ~2–3 kg with placebo (around a 3 kg difference).

• Other data show improved weight loss and metabolic markers in people with type 2 diabetes and prediabeteswhen orlistat is used for 12+ weeks.

Realistically, that often translates to an extra 2–3% of body weight on top of what you achieve with diet and exercise alone.

NHS guidance usually states that treatment should be stopped if you haven’t lost around 5% of your starting weight after 3 months on full-dose orlistat – because you’re unlikely to benefit long-term.

Orlistat how does it work in practice? (Diet, dosing, timing)

The usual orlistat dose is:

• Xenical / generic 120 mg:

  • One 120 mg capsule with each main meal containing fat (up to three times a day)

• Alli 60 mg:

  • One 60 mg capsule with each fat-containing meal, up to three times a day

Important practical points:

• Take the capsule during the meal or up to 1 hour after.

• Skip the dose if you miss a meal or eat a meal with no fat – orlistat only works on dietary fat.

• Aim for no more than ~30% of your calories from fat, and avoid very high-fat meals – this massively reduces side-effects.

You’ll often see “orlistat diet” advice from NHS dietitians emphasising:

• Lean protein

• Plenty of vegetables and fibre

• Limited oils, fried foods, creamy sauces, processed meats

• Watching out for “hidden” fat in pastries, takeaways, cheese, etc.

Side-effects: the honest truth about orlistat weight loss pills

The downside of blocking fat in the gut is that unabsorbed fat has to go somewhere – namely, out through your bowels.

Common GI side-effects

Typical orlistat side-effects include:

• Oily or fatty stools (orange/oily droplets in the toilet bowl)

• Urgency to open your bowels

• Increased frequency of bowel movements

• Flatulence with oily spotting

• Diarrhoea or loose stools

• Abdominal pain or cramping

These are usually mild to moderate, and are much worse if you eat:

• High-fat meals (fried foods, takeaways, creamy dishes)

• Large portions of cheese, chocolate, pastries, etc.

NHS and dietetic leaflets are very clear:
Follow a low-fat diet, and these effects often settle over time and remain manageable. Ignore the diet advice, and you’re more likely to get unpleasant accidents.

Less common but important risks

Less common issues include:

• Possible fat-soluble vitamin deficiency (A, D, E, K) with long-term use – sometimes doctors recommend a multivitamin taken at bedtime away from doses

• Rare cases of liver injury or gallbladder issues reported

• Potential for kidney stones, particularly in people with pre-existing kidney disease

Because of this, orlistat is usually avoided or used cautiously in people with:

• Chronic malabsorption syndromes

• Cholestasis

• Significant kidney or liver disease

• Certain interactions (e.g. ciclosporin, warfarin, levothyroxine – your doctor/pharmacist will check)

Orlistat reviews: before and after experiences (what people actually say)

Looking across orlistat reviews, clinic blogs and patient info sites, a few themes appear consistently:

Positives people mention

• “It keeps me in check with my diet.”
  Knowing that high-fat meals will likely cause side-effects pushes many users to avoid takeaways and greasy foods.

• Steady, modest weight loss – often a few kilos over months, especially when combined with sustained dietary changes.

• Some report improved cholesterol and blood glucose alongside weight loss.

Frustrations and negatives

• Embarrassing GI side-effects in the first weeks, or when they slip up on the diet

• The need to plan toilet access early on until they know how their body reacts

• Weight loss that is slower and more modest than they hoped (especially when comparing themselves to dramatic GLP-1 results)

• Regain of weight if they stop orlistat and relax diet habits

Overall, orlistat weight loss reviews before and after tend to highlight that it’s:

A helpful nudge and safety net for fat intake, not a miracle pill – and it punishes greasy “cheat meals” more than anything else.

Buying orlistat / Xenical online: what’s safe and what’s not?

You’ll see many adverts to buy orlistat online, buy Xenical online, or orlistat online cheap. In the UK, there are safe and unsafe ways to do this.

Safe routes (UK-regulated)

Legitimate online services will:

• Be registered with the GPhC (pharmacy regulator) and list their registration number

• Require a medical questionnaire (BMI, health conditions, other meds)

• Have each order reviewed by a prescriber (GP or independent prescriber)

• Dispense licensed Xenical / generic orlistat 120 mg or Alli 60 mg via a UK pharmacy

• Provide clear guidance on diet, side-effects and when to stop

Red flags

Avoid websites that:

• Offer orlistat pills with no questions asked

• Don’t show clear pharmacy and prescriber details

• Ship from outside the UK/EU without proper regulation

• Use unusually low prices for “Xenical 120 mg capsules” or “Alli weight loss pill” compared to UK averages

• Sell “orlistat” as part of “herbal” or “detox” blends without proper licensing

If in doubt, get orlistat tablets through your GP, local pharmacy or a well-known online doctor/pharmacy you can verify.

Orlistat vs newer options (and where it fits in a modern plan)

In modern UK obesity care, orlistat is one tool among many:

• Orlistat (Xenical/Alli) – fat-blocking pills, modest effect, GI-heavy side-effect profile

• GLP-1 injections (e.g. Wegovy, Saxenda) – more powerful appetite-based weight-loss treatments, but injectable and prescription-only

• Lifestyle programmes – diet, physical activity, behavioural support

• Other medicines like Mysimba (naltrexone/bupropion) in selected patients

For some people, especially those:

• With GI sensitivities or malabsorption

• On multiple interacting meds

• Or very high cardiovascular risk

…a GLP-1 option might be preferable. For others who don’t want injections or can’t access them, orlistat tablets remain a reasonable, evidence-based option, as long as expectations are realistic.

On your site, you’d usually link out to:

• The GLP-1 hub article (Wegovy/Saxenda/Ozempic/semaglutide overview)

• Individual Wegovy and Saxenda deep-dives

to help readers compare options.

Key takeaways

• Orlistat, Xenical and Alli are all orlistat weight loss pills – a fat-blocking medicine that reduces absorption of dietary fat in the gut.

• Xenical 120 mg (and generic orlistat 120 mg) are prescription only, usually for adults with BMI ≥ 30 or ≥ 28 with risk factors. Alli 60 mg is a pharmacy/OTC option for adults with BMI ≥ 28.

• Typical weight loss is modest (an extra ~2–3 kg over several months vs lifestyle alone), but this can still be clinically meaningful, especially for metabolic health.

• The main trade-off is GI side-effects: oily stools, urgency and diarrhoea if you eat high-fat meals – which is why a low-fat diet is essential.

• Always use regulated UK routes (GP, NHS services, or verified online/pharmacy providers) when you buy orlistat or Xenical online, and avoid “no-questions” or very cheap offers.

If you’re considering orlistat tablets as part of your weight-loss journey, the safest next step is a doctor or pharmacist consultation to check:

• Whether you meet BMI and health criteria

• Which version (Xenical vs Alli vs other options) fits you best

• How to adapt your diet to reduce side-effects and get the best results.