Wegovy or Mounjaro: How to Think Through the Choice

Step 1: understand what makes them different under the hood

Wegovy contains semaglutide, a GLP-1 receptor agonist. GLP-1 is a gut hormone that signals fullness, slows the rate at which your stomach empties and plays a role in blood-sugar regulation. The medicine mimics that signal in a sustained, once-weekly way. You can read a full clinical overview on the semaglutide treatment page, but the short version is that in the landmark STEP 1 trial (68 weeks, adults with obesity and no diabetes) participants on 2.4 mg semaglutide lost an average of around 15% of their body weight, as reported in the New England Journal of Medicine (STEP 1, 2021).

Mounjaro contains tirzepatide. It activates both GLP-1 and GIP receptors simultaneously — GIP being a second gut hormone that works through a different but complementary pathway. That dual action appears to produce stronger appetite suppression for many people. In the SURMOUNT-1 trial (72 weeks, 2,539 adults), average weight reduction at the highest dose reached around 20–21%. Then came SURMOUNT-5: a direct head-to-head comparison of tirzepatide and semaglutide 2.4 mg, published in the New England Journal of Medicine in 2025, which found tirzepatide produced greater average loss over 72 weeks. NICE referenced those indirect and direct comparisons in its technology appraisal of tirzepatide, see NICE TA1026 for the full analysis.

The practical upshot: on average, Mounjaro tends to produce larger weight reduction than standard-dose Wegovy. That said, individual responses vary, and trial averages describe populations, not individuals.

Step 2: check whether you meet the eligibility criteria for each

The licensed eligibility criteria for both medicines are broadly similar. Adults with a BMI of 30 or above qualify, as do adults with a BMI of 27 or above who have at least one weight-related health condition, for example, high blood pressure, type 2 diabetes, obstructive sleep apnoea or high cholesterol. Lower BMI thresholds can apply for some ethnic backgrounds under UK guidance; your prescriber will apply these correctly.

A few differences are worth knowing. Wegovy is also licensed for reducing cardiovascular event risk in certain adults, and from July 2026 holds a conditional UK approval for a form of fatty liver disease (MASH). Mounjaro is also licensed for type 2 diabetes management. These additional indications do not change the weight-management eligibility criteria, but they can influence which medicine fits a person's broader health profile.

For a fuller picture of how the two medicines compare on eligibility, mechanism and evidence, our Wegovy versus Mounjaro comparison page goes through the detail. And if you are wondering whether they are essentially the same product under different names, our page on whether Wegovy and Mounjaro are the same medicine clears that up clearly.

Step 3: factor in practical considerations, routine, tolerance and existing medicines

Both are once-weekly subcutaneous injections. Both start at a low dose to let your system adjust, then titrate upward every four weeks or so, guided by your prescriber. Mounjaro comes in a KwikPen (each pen holds four doses); Wegovy comes in a single-use pre-filled pen. Both need to be kept in the fridge, slotting the box into the fridge door alongside everyday staples tends to be the routine that sticks for most people.

Side effects overlap considerably: nausea, vomiting, diarrhoea, constipation and indigestion are the most commonly reported for both, and they tend to be most noticeable when starting or after a dose increase, often settling within a couple of weeks. The NHS medicines pages for tirzepatide and semaglutide cover the full side-effect profiles clearly.

One clinically important practical note: women using oral contraceptives alongside Mounjaro are advised to add a non-oral method of contraception for the first four weeks of treatment and for four weeks after each dose increase, because tirzepatide's effect on gastric emptying may reduce pill absorption. The same recommendation applies in the same circumstances with each dose change. There is no equivalent evidence-based warning for Wegovy in this regard. This is a conversation to have with your prescriber; they will factor in your contraception at the assessment stage. For more on this and related practical questions, our Wegovy treatment page has a dedicated section.

Existing medicines matter too. Both require prescriber review of your current medication list. Neither is suitable during pregnancy, breastfeeding or when trying to conceive. Neither is licensed for people under 18. Anyone with a personal or family history of medullary thyroid carcinoma or MEN2 should not use either medicine.

Step 4: think about cost and access in the right order

NHS access to both medicines exists but is restricted and phased. Mounjaro on the NHS currently requires a BMI of 40 or above with four or more qualifying conditions (a second cohort covering BMI 35–39.9 opened in June 2026). Wegovy on the NHS is routed through specialist weight management services with typically long waiting times. If you do not meet NHS criteria or prefer not to wait, a regulated private pharmacy is a legitimate route, provided it is one you can verify on the GPhC register.

Private costs have shifted since Eli Lilly raised Mounjaro's UK list price in September 2025, with typical private prices reported at roughly £149–£375 per month depending on dose and provider. Our Wegovy pricing page covers the cost landscape honestly, and our weight-loss treatment overview sets out how both medicines sit within a broader approach to weight management. At nume, one transparent price covers consultation, prescription, treatment and next-working-day delivery, no subscription, no hidden fees. We are not the cheapest option out there. That is a deliberate choice.

If you are ready to find out which medicine your prescriber would recommend for your specific circumstances, check your eligibility with a free consultation. A GPhC-registered Independent Prescriber (a real clinician, not an algorithm) reads your answers and responds the same day. You can also find more detail about how the treatment works in practice on our Manjaro Wegovy page, which covers the two medicines side by side.