Mysimba vs Orlistat: All You Need to Know

Several weight-loss treatments are currently available on the UK market. Some big names include Wegovy and Mounjaro, and their prominence means there's already a ton of information about them. Mysimba and Orlistat are less frequently discussed, but are no less important. People use them every day, or have used them in the past, and both have been proven effective for reducing weight. But how exactly do they work? Which one is more effective? Which one is right for you?

This article covers Mysimba vs Orlistat in detail, giving a comprehensive overview of each and a running comparison, so if you are debating between the two, you will come out well informed and confident in your knowledge of both.

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What are Mysimba and Orlistat?

Mysimba and Orlistat are both weight-loss treatments, and two of the oldest still available on the UK market. Their age does not reduce their effectiveness, and both can work extremely well when paired with other healthy practices like an improved diet and regular exercise. Mysimba and Orlistat are administered orally and multiple times a day, though Mysimba increases in potency over its dosing schedule, while Orlistat may stay at the same potency and frequency.

Unlike many weight-loss treatments on the UK market, neither Mysimba nor Orlistat is a ‘GLP-1’ medication. These treatments, including Foundayo, Mounjaro, and Wegovy, work mainly in the stomach, slowing gastric emptying and keeping you full for longer. As you will see, Mysimba and Orlistat work in more unique ways.

Mysimba vs Orlistat at a Glance

We'll discuss the differences in the table below later in this article, with more substantial ones, like side effects and dosing schedules, getting their own dedicated subsections. If you prefer just the stats, then the table provides an overview of the two treatments. If not, keep reading to learn more.

How Do They Work?

Mysimba contains the two active ingredients naltrexone and bupropion, which have the combined effects of reducing the positive feelings associated with overeating. They target two different receptors in the brain to reduce dopamine released after eating a large or tasty meal, which in turn lessens cravings for indulgent food. Less desire to overeat means less overeating, which means a lower caloric intake.

Orlistat, and its branded versions Alli and Xenical, work differently. Instead of acting in the brain, they act directly on the stomach and digestive tract. It has a single active ingredient, orlistat, that blocks some fat absorption when you eat fatty foods. Less fat entering the body also reduces calories, so both treatments have fairly similar outcomes. The branded version, Alli, contains 60mg of Orlistat and can be bought over the counter, whereas Xenical and Orlistat as a standalone contain 120mg and require a prescription.

Orlistat vs Mysimba: Which is More Effective?

In general, Mysimba tends to be more effective than Orlistat, even at its 120mg dosage. 55% of people on Mysimba lost 5% or more of their total body weight, compared to 44% on Orlistat. Both will require lifestyle changes to be at their most effective, though.

Side Effects of Orlistat and Mysimba

Like any medical treatment, Orlistat and Mysimba can cause unwanted side effects, and you should know what to expect before committing to either treatment. The common (affecting up to 1 in 10) and very common (affecting more than 1 in 10) side effects of the treatments are:

A full list of Mysimba’s side effects is available in its Patient Information Leaflet. The same goes for Alli and Xenical.

Mysimba and Orlistat Dosage Schedules

Mysimba has a strict daily dosage escalation schedule that must be followed. Orlistat can be taken with a little more leniency.

The Mysimba dosage schedule is shown in the image below. You will start the treatment by taking one pill a day, and after one week of this, you will increase to two a day, then three, then four by the time you end your first month. After this, you will remain on four pills a day for the remainder of the treatment. The schedule goes like this:

• Week 1 - One tablet every morning
• Week 2 - Two tablets daily, one in the morning, one in the evening
• Week 3 - Three tablets daily, two in the morning, one in the evening
• Week 4 - Four tablets daily, two in the morning, two in the evening

If you miss a dose of Mysimba, you should take your next dose at your usual time. Never take two doses at once to make up for a missed one.

Orlistat is taken once, twice, or up to three times daily, at your discretion, depending on the meals you have had or plan to have. Unlike Mysimba, which has specific instructions for what to do if you miss a dose, you do not need to take Orlistat after every meal. You should take it if your meal contains fat - if it doesn’t, then there’s no need to take any Orlistat.

Mysimba or Orlistat: Which is Right For Me?

Many factors go into choosing the right weight-loss treatment, and it is not a decision to take lightly.

Cost is one factor, and Orlistat has the advantage here, as it is the cheaper option. Orlistat is also more versatile, as you can take it or not take it depending on what you eat, whereas Mysimba has a stricter dosage schedule. The ingredients also matter, as you may be allergic to one of the treatments.

If you ever need advice, information, or just someone to talk to, our clinicians are here to help. They can review your current situation and medical background to ensure you get the treatment best suited to you.

Can You Take Mysimba and Orlistat Together?

Unless allowed by your clinician, you should not take Mysimba and Orlistat at the same time. In fact, there are very few weight-loss treatments that you can take at the same time, as this could lead to adverse and severe side effects. The two medications could interact in unpleasant ways. If unsure, always ask a clinician.

Are There Any Alternatives?

Yes, multiple other weight-loss pills are available on the UK market and at Prescription Doctor, as well as other treatment types such as injections. Foundayo is the most recently released weight-loss pill, with an effectiveness rate of 12.4%. Wegovy injections are now available as Wegovy pills too, and they show about 16.6% weight loss. We have a comprehensive overview of all available weight loss pills here.

The ‘Stats and The Facts

With Prescription Doctor, you don't need to fret about which treatment is best for you. It’s okay to be unsure, because you’ll never have to decide alone. Our talented team of clinicians is always ready to help wherever you need it, from choosing a treatment to side effects, dosage scheduling, and usage instructions.

Both Mysimba and the branded forms of Orlistat are approved for sale in the UK. We’ve helped people since 2013, with our clinicians supporting you every step of the way, monitoring your progress and making sure you’re doing okay. Start your weight-loss consultation today by filling out a short online form, and we’ll get things sorted for you.

Authored & Reviewed By

Mohamed Imran Lakhi

MPharm - Lead Pharmacist

Imran Lakhi is the superintendent pharmacist and founder at Prescription Doctor. He has been at the core of our team.

Published on: 02/11/2026 Reviewed on: 02/11/2026