Does Wegovy Work Like Mounjaro, or Are They Built Differently?

Step 1, Understand what each medicine actually does in your body

Wegovy (semaglutide 2.4mg, and now up to 7.2mg) binds to one receptor: the GLP-1 receptor. That is the receptor responsible for telling your brain you have eaten, slowing gastric emptying and reducing appetite. It does this job well. The STEP 1 trial published in the New England Journal of Medicine found an average body-weight reduction of around 15% over 68 weeks at the 2.4mg maintenance dose.

Mounjaro binds to the same GLP-1 receptor and, on top of that, the GIP receptor, a second gut hormone involved in insulin secretion, fat storage and satiety. Whether that extra receptor activation is clinically meaningful was debated until the SURMOUNT-1 trial reported average weight reductions of around 20–21% at the 15mg dose over 72 weeks, and the SURMOUNT-5 head-to-head trial (published in the New England Journal of Medicine in 2025) showed tirzepatide producing greater average weight loss than semaglutide 2.4mg directly. If you are wondering whether Wegovy works the same way as Mounjaro at a mechanistic level, we cover that question in detail separately. If you want to read more about whether that difference holds up in practice, our comparison of real-world effectiveness goes further on this.

Practically speaking: both medicines slow the speed at which food passes from your stomach. Both reduce how much you want to eat. The difference is one of degree, not of kind, and neither replaces the diet and activity changes you make alongside treatment.

Step 2, Check the licensed doses and eligibility criteria side by side

Both treatments start at a low dose to help your system adjust; neither starting dose is the therapeutic dose. The titration schedule is set by the prescriber, not something to self-direct. Lower BMI thresholds apply for South Asian, Chinese, Middle Eastern, Black African and African-Caribbean backgrounds under UK guidance. The NICE appraisal of tirzepatide (TA1026) and the NICE appraisal of semaglutide (TA875) set out the NHS eligibility criteria in detail; private eligibility follows the licensed indications in the SmPCs.

A quick self-check you can do right now: the NHS BMI calculator takes under a minute and tells you whether your BMI sits in the range where either medicine is licensed. That is your first data point before a consultation.

Step 3, Weigh up the side-effect profiles

The side-effect landscape is similar for both. Gastrointestinal effects (nausea, diarrhoea, constipation, burping, indigestion) are the most commonly reported with each, and tend to be most noticeable after a new dose starts, settling over days to a couple of weeks for most people. The NHS medicines page for tirzepatide lists the full profile; the equivalent semaglutide page covers Wegovy's.

There are differences in frequency rather than type. Some people find one medicine easier to tolerate than the other. That is not something a head-to-head chart can predict for any individual, it becomes clear during treatment. Both carry a small, infrequent risk of acute pancreatitis; seek urgent medical help for severe stomach pain that radiates to the back, with or without vomiting. Both are Black Triangle medicines, meaning the MHRA requests that healthcare professionals report any suspected adverse reactions.

Neither medicine is recommended during pregnancy, while breastfeeding, or for anyone under 18. The tirzepatide prescribing guidance also notes that women taking oral contraceptives should use an additional non-oral method for the first four weeks of treatment and for four weeks after each dose increase, because gastric emptying changes may reduce pill absorption. That is one practical difference between the two that our side-by-side overview explores in more detail.

Step 4, Understand what a clinical decision actually involves here

Reading a comparison table is useful. It cannot do what a prescriber does. A clinician looks at your weight history, current medications, any relevant conditions, how you responded to previous treatment, and only then recommends which medicine, at which starting dose, is the right fit.

At nume (at who we are and how our pharmacy works) every consultation is personally read by a GPhC-registered Independent Prescriber the same day. No algorithm makes the call. If you have already been on one of these medicines and are wondering whether to switch, our page on how Wegovy performs after a course of Mounjaro addresses that specific question. For a fuller breakdown of the price implications of choosing between them, the cost comparison is worth reading before your consultation. If you are trying to decide between the two and want a direct answer on whether Wegovy works as well as Mounjaro for weight loss, that page brings together the trial evidence and practical considerations in one place.

Which medicine suits you is a clinical decision our prescribers make with you. The starting point is a free consultation, with no obligation until you and the prescriber agree on a plan.