Orlistat vs Mounjaro: Which Suits You? (October 2026)

01 · The verdict

Orlistat vs Mounjaro: who each option suits

Mounjaro suits adults who meet the licensed criteria and want a treatment that acts on appetite; orlistat suits people whose prescriber prefers a tablet that works in the gut. Your prescriber decides, based on your medical history, current medications and goals, not on the headline number alone.

Mounjaro (tirzepatide) is licensed in the UK for weight management and type 2 diabetes.¹ Orlistat (tablet) blocks some dietary fat absorption and produces smaller average losses. You can read about the Xenical (orlistat 120mg) product or browse all weight loss treatments to see how the options sit together.

02 · Side by side

Orlistat vs Mounjaro comparison table

The XENDOS and SURMOUNT-1 trials had different designs, populations and lengths, so their results should not be set against each other.

03 · Cost

What Mounjaro costs

A 2.5mg Mounjaro pen costs £169.99 per month at standard price, and the £189.99 5mg pen follows once your prescriber steps you up. A new customer's first 2.5mg pen costs £129.99 with code FIRST40. Every later order is £25 off the standard price (code DOSE25). You can see current doses and availability on the Mounjaro pen page; all six doses are in stock. Prices checked 24 October 2026.

Related guide: Can You Take Metformin & Orlistat Together? Orlistat vs Xenical.

Related guides: Can You Take Orlistat & Wegovy Together? Cheapest UK and Can You Take Orlistat & Metformin Together? UK Pharmacy.

04 · Weight loss results

Weight loss results in clinical trials

In SURMOUNT-1, 2,539 adults taking tirzepatide alongside diet and exercise lost on average 15% of body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, compared with 3.1% with lifestyle changes alone.² For someone starting at 100 kg, 20.9% is about 21 kg. These are trial averages, individual results vary, and treatment works alongside a reduced-calorie diet and increased physical activity.

At 72 weeks, 85% of participants on 5mg, 89% on 10mg and 91% on 15mg had lost at least 5% of their body weight.²

For orlistat, the four-year XENDOS trial of 3,305 adults found that people taking orlistat alongside lifestyle changes lost on average 5.8 kg, compared with 3.0 kg on placebo. Orlistat is therefore associated with smaller average losses. Trial averages do not predict your own result.

The first large head-to-head trial, SURMOUNT-5, compared tirzepatide with semaglutide 2.4mg (Wegovy), not with orlistat. Tirzepatide users lost on average 20.2% of body weight over 72 weeks versus 13.7%.¹⁵

05 · Taking them together

Can you take orlistat with Mounjaro?

Whether you can take orlistat and Mounjaro together is a question for your prescriber, who reviews your whole medicines list before deciding. Tell them if you already take orlistat, or if you are thinking of adding it, before you start or change anything.

Orlistat is not a GLP-1 medicine. Mounjaro must never be combined with other GLP-1 medicines, unlicensed "research" peptides such as retatrutide (which has no UK licence) or compounded copies, because these combinations have no safety data and no regulated supply chain. If something promises faster results outside a licensed pathway, that is the warning sign.

If you take insulin or a sulfonylurea alongside Mounjaro, watch for low blood sugar (shakiness, sweating, confusion); your prescriber may need to adjust those medicines. Our page on Mounjaro and glipizide covers that situation.¹³

06 · Side effects and safety

Side effects and when to seek help

Most Mounjaro side effects are digestive. The most common, affecting more than 1 in 10 people, are nausea, diarrhoea, vomiting, constipation and abdominal discomfort. Common effects (up to 1 in 10) include indigestion, reduced appetite, dizziness, reflux, burping, hair shedding and injection-site reactions. They are most likely when starting or moving up a dose, and for most people ease within days to a few weeks.¹³

Serious side effects are uncommon but need urgent attention. Seek immediate medical help for:

• severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis);
• pain in the upper right abdomen, fever or yellowing of the skin or eyes (possible gallbladder problems);
• signs of a severe allergic reaction, such as swelling of the face or throat and difficulty breathing.

You can report any suspected side effect through the Yellow Card scheme.¹⁹ For orlistat, read the patient leaflet that comes with it and ask your pharmacist or prescriber about its side effects.

Mounjaro slows stomach emptying, which can reduce how well oral contraceptive pills are absorbed. Mounjaro must not be used during pregnancy, and it should be stopped at least one month before trying to conceive. If you become pregnant during treatment, stop the medicine and tell your prescriber promptly. The SmPC advises switching to a non-oral method, or adding a barrier method such as condoms, for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase.¹ Mounjaro must not be used during pregnancy, and it should be stopped at least one month before trying to conceive. If you become pregnant during treatment, stop the medicine and tell your prescriber promptly.

07 · How treatment works day to day

Dosing, storage and NHS access

Mounjaro starts at 2.5mg once weekly, with at least 4 weeks on each dose, depending on how you respond. Your prescriber guides each step up. Keep pens in a fridge at 2–8°C and never freeze them. Once in use, a pen can be kept out of the fridge not above 30°C for up to 30 days, then discarded.¹

Mounjaro is available on the NHS, but access is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the primary-care rollout began in June 2025 with the highest-need groups first.⁴ Many people who meet the licensed criteria choose regulated private treatment rather than wait.

Our service includes a free consultation reviewed by a GPhC-registered prescriber, official LillyDirect supply, free next-day tracked delivery and ongoing monthly reviews. You can start your free consultation to see whether Mounjaro is suitable. Mounjaro is a prescription-only medicine used alongside a reduced-calorie diet and increased physical activity.