Going straight from Mounjaro to Wegovy: what actually happens

Step 1, why you cannot simply continue at the same number

Mounjaro (tirzepatide) activates two receptors: GIP and GLP-1. Wegovy (semaglutide) activates only the GLP-1 receptor. Because of that difference in mechanism, the dose numbers on each pen do not translate across. A 10mg Mounjaro dose does not equal 1.7mg or 2.4mg Wegovy in any meaningful pharmacological sense, so there is no published conversion table a prescriber can reach for.

In practice, most clinicians treat a switch as a new titration rather than a continuation. That typically means starting Wegovy at a lower dose than you might expect (sometimes at or near the beginning of the schedule) and working up again. This is not a setback; it is how the medicine is designed to be introduced safely. The graduated approach exists to manage the gastrointestinal side effects that tend to be most noticeable at the start of semaglutide treatment. You can read about what the move from Mounjaro to Wegovy involves in more detail, but the practical takeaway is clear: do not assume the highest dose you reached on Mounjaro is where you will land on Wegovy.

The licensed titration pathway for Wegovy runs from 0.25mg up through 0.5mg, 1.0mg and 1.7mg to the 2.4mg maintenance dose, each step roughly four weeks apart, guided by your prescriber. The NHS semaglutide page sets out what to expect at each stage.

Step 2, what to check before you switch

Before anything else, confirm your reason for switching. Common ones include: Mounjaro supply issues, a preference to move to a single-receptor medicine, a clinical recommendation from a prescriber, or a cost consideration. The price difference between Mounjaro and Wegovy is real and worth understanding, but cost alone is not a clinical justification, a prescriber still needs to assess whether Wegovy is appropriate for you specifically.

One practical step you can do right now: pull up the GPhC pharmacy register entry for nume and confirm you are dealing with a registered pharmacy before sharing any medical information. It takes under a minute and is the single fastest way to verify a UK online pharmacy is operating legally. Any provider offering to switch your prescription medicine without a full clinical review is not following the rules.

You will also need to think about timing. There is no mandatory washout period between tirzepatide and semaglutide, but your prescriber may choose to time the switch relative to your last injection to minimise overlapping side effects. That is a clinical call, not a self-managed one. If you are curious whether taking both at the same time is ever appropriate, the short answer is no.

Step 3, comparing the two treatments before you decide

It is worth understanding what you are moving between. The table below summarises the key factual differences, to give your conversation with a prescriber a useful starting point.

The SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025, remains the strongest direct comparison available, and NICE's appraisal of tirzepatide (TA1026) notes that indirect comparisons broadly favour it. That said, head-to-head evidence at the 7.2mg Wegovy dose is limited, and individual response varies. If you have been wondering whether Zepbound is a semaglutide, it is worth clarifying before comparing products, as the answer shapes how you read the trial data. For a fuller breakdown, the Wegovy versus Mounjaro comparison page covers the evidence in more depth.

Neither medicine is better for everyone. Which suits you is a clinical decision our prescribers make with you, based on your history, your current dose, and your goals. Start a free consultation and a GPhC-registered prescriber will review your case the same day.