Medicines Similar to Mounjaro: What the Evidence Actually Shows

What the head-to-head trial found when tirzepatide met semaglutide

The SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025, ran for 72 weeks across 751 adults with obesity and no diabetes. Participants received either tirzepatide or semaglutide 2.4mg alongside lifestyle changes. Tirzepatide produced greater average weight loss. That single finding matters because, until that trial, the comparison had only been possible by looking across two separate studies with different populations, an apples-to-pears exercise that any statistician would caution against.

The gap is real but not enormous, and it narrows further with the newer Wegovy 7.2mg dose, a single higher-dose pen the MHRA approved in April 2026, which achieved around 20.7% average weight loss over 72 weeks in its own trials, approaching tirzepatide 15mg results. So the evidence landscape is still shifting. Which result a given person sees depends on their own biology, adherence, diet and activity, things a trial average cannot capture.

For context on the tirzepatide evidence base as a whole, the SURMOUNT programme enrolled thousands of adults across multiple trials, producing the largest dataset for any licensed weight-management medicine in the UK at the time of Mounjaro's approval.

The mechanism gap: why 'similar' doesn't mean 'the same'

Semaglutide is a GLP-1 receptor agonist. Tirzepatide is a dual GIP and GLP-1 receptor agonist, the only medicine of that type licensed for weight management in the UK. GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 are both gut hormones involved in appetite signalling and blood-sugar regulation, but they act on different receptors, and combining them appears to produce a larger effect on appetite suppression and slowing of gastric emptying than GLP-1 activation alone.

That difference in mechanism is why regulators, prescribers and trial designers treat them as related but distinct medicines rather than interchangeable ones. It also explains why someone who did not respond well to semaglutide might respond differently to tirzepatide, and vice versa, though a prescriber would be the right person to assess whether switching makes sense in any individual case.

Ozempic, which you may have seen mentioned alongside both medicines, is also semaglutide, but it is licensed for type 2 diabetes, not weight management. It is not a licensed alternative for weight loss, and presenting it as one would be misleading. The distinction matters when you are reading about what is similar to Mounjaro in a weight-management context.

What about an oral option, is there anything similar without an injection?

The MHRA approved oral semaglutide tablets (Wegovy tablets) on 11 June 2026, making the UK the first country in Europe to licence an oral GLP-1 medicine for weight management. The escalating schedule runs from 1.5mg daily up to a 25mg maintenance dose, taken first thing on an empty stomach with a small amount of plain water, at least 30 minutes before food or other medicines. The OASIS 4 trial found around 13.6% average weight loss over 64 weeks versus placebo.

For people who are averse to injections, the oral tablet is the closest licensed alternative to the injectable options, though the average weight-loss figure sits below what the injections achieve. There is no oral tirzepatide licensed for weight management in the UK as of mid-2026; the page on oral tirzepatide covers the current development picture for that compound specifically.

Cost is one factor people weigh up when exploring alternatives. The page covering Mounjaro's UK pricing history sets out the context around Eli Lilly's list-price changes from September 2025 onward, which is worth understanding before comparing options.

Biosimilars, unlicensed products and what to look out for

A biosimilar version of a medicine goes through a separate regulatory approval process, it cannot simply be assumed to be equivalent without that scrutiny. No biosimilar tirzepatide has been approved by the MHRA, and the Mounjaro biosimilar page explains what that approval process would involve and why anything marketed as one now sits outside the licensed supply chain.

The MHRA has taken enforcement action on a significant scale: around 20 million doses of illegally traded weight-loss medicines, worth roughly £45 million, were seized in 2025 alone, including counterfeit tirzepatide pens from an unlicensed manufacturing site in the UK. Anyone sourcing medicines that look similar to Mounjaro or Wegovy from sellers without a verifiable prescription process is taking a serious risk. The guide to tirzepatide-similar products covers how to tell legitimate supply from unlicensed versions.

One quick check worth doing before ordering anything from any online pharmacy: visit the GPhC register at pharmacyregulation.org/registers and search by the pharmacy's name or registration number. It takes under a minute and tells you whether the pharmacy is registered and currently compliant. Worth checking.

The overview of medicines in the same drug class as Mounjaro goes into more detail on related compounds. And if you are exploring your options more broadly, the weight-loss treatment overview covers everything currently available through a licensed route in the UK. When you are ready to find out which option suits your circumstances, you can check your eligibility through a free consultation with our prescribers.