Switching From Mounjaro to Wegovy and What Dose to Start On

Switching from Mounjaro to Wegovy has no labelled dose conversion: the UK Wegovy starting schedule begins at 0.25 mg once weekly (Wegovy SmPC, section 4.2). On a half-life estimate, about 38% of the tirzepatide level just after your last Mounjaro dose is still there 7 days later (Mounjaro SmPC, section 5.2). If Wegovy starts that day, its first 0.25 mg dose reaches an estimated 5% of the level that weekly 2.4 mg doses settle at (Wegovy SmPC, sections 4.2 and 5.2).

Key facts

• Wegovy increases through 0.25, 0.5, 1 and 1.7 mg at 4-week intervals, reaching 2.4 mg from week 17 (Wegovy SmPC, section 4.2).
• Tirzepatide’s half-life is approximately 5 days, compared with about 1 week for semaglutide (Mounjaro SmPC, section 5.2; Wegovy SmPC, section 5.2).
• Semaglutide remains in circulation for approximately 7 weeks after the last Wegovy 2.4 mg dose (Wegovy SmPC, section 5.2).
• SURMOUNT-5 reported weight loss of 20.2% with tirzepatide and 13.7% with semaglutide at 72 weeks, but did not test switching (trial publication).
• The NHS list price of a Mounjaro 12.5 mg or 15 mg KwikPen rose from £122 to £330 per pen from September 2025 (NHS Business Services Authority).

Is there a Mounjaro to Wegovy (semaglutide) dose conversion?

There is no labelled Mounjaro to Wegovy dose conversion; Wegovy’s starting schedule begins at 0.25 mg once weekly (Wegovy SmPC, section 4.2). The Mounjaro SmPC has no switching rule for another GLP‑1 medicine either, so neither label gives a Mounjaro to semaglutide conversion (Mounjaro SmPC, section 4.2).

The UK Wegovy ladder specifies the following doses and weeks (Wegovy SmPC, section 4.2).

A first Wegovy dose above 0.25 mg departs from the SmPC schedule; it is not a conversion (Wegovy SmPC, section 4.2).

The SmPC states, “To reduce the likelihood of gastrointestinal symptoms, the dose should be escalated over a 16-week period” (section 4.2).

The Wegovy SmPC’s only switching rule is for semaglutide 25 mg tablets, which can move to the 2.4 mg injection the day after the last tablet (section 4.2).

Compare the full Wegovy and Mounjaro dose ladders when you need a chart of schedules for switching between GLP‑1 agonists. Once your Wegovy starting date is set, the dose titration planner helps lay out the dates of each step.

How long after stopping Mounjaro can you start Wegovy?

Neither UK SmPC specifies a waiting period for switching from tirzepatide to semaglutide (Mounjaro SmPC, section 4.2; Wegovy SmPC, section 4.2). Starting on the day your next Mounjaro dose would have been due keeps your weekly injection day. The table below uses that day.

If your plan starts Wegovy 7 days after Mounjaro, an estimated 38% of the tirzepatide level remains, using its approximately 5-day half-life (Mounjaro SmPC, section 5.2). The same half-life model estimates about 14% remaining after 14 days and 5% after 21 days (Mounjaro SmPC, section 5.2).

Each percentage is a share of the level just after your last Mounjaro injection.

Once you have started, a late or missed Wegovy dose follows the missed-dose rules for Wegovy, not the switching timetable.

What happens to Mounjaro and Wegovy levels week by week?

Mounjaro levels decline with tirzepatide’s approximately 5-day half-life, while Wegovy builds with semaglutide’s approximately 1-week half-life (Mounjaro SmPC, section 5.2; Wegovy SmPC, section 5.2). The switch is an overlap of one falling level and one rising level.

The table assumes your first Wegovy injection is 7 days after the last Mounjaro dose, followed by the labelled Wegovy ladder (Wegovy SmPC, section 4.2). Each row is measured just after that week’s Wegovy injection.

The derived estimates add up what remains of every dose, halving each amount once per half-life, with no absorption phase, using the dosage plotter’s method. Those half-lives are about 5 days for tirzepatide and about 1 week for semaglutide.

The columns use different reference levels. Tirzepatide is compared with its level just after your last Mounjaro dose. Semaglutide is shown against the level just after a 2.4 mg dose once weekly doses have levelled off. You cannot add the percentages.

A 2.4 mg first dose reaches an estimated 50% of the 2.4 mg steady-state level, against about 5% for 0.25 mg (Wegovy SmPC, section 5.2). On that modelled 2.4 mg start, the estimate reaches 94% after dose 4 (Wegovy SmPC, section 5.2).

Because the model has no absorption phase, the table shows calculated amounts just after each injection, not measured blood levels. A delayed Wegovy step-up would change the semaglutide column.

In week 2, the model puts tirzepatide at about 14% of its last post-dose level and semaglutide at about 8% of the 2.4 mg level (Mounjaro SmPC; Wegovy SmPC). By week 4, the estimates are about 2% and 10% respectively (Mounjaro SmPC; Wegovy SmPC). Weeks 2 to 4 are when both estimated levels are lowest at the same time. The model estimates drug levels, not hunger.

Use the GLP‑1 dosage plotter to explore the estimated curves using your own injection dates.

You can log your last Mounjaro shot and each Wegovy shot in Pensday, which works with both and draws a free estimated medication-level curve by day since injection for tirzepatide and semaglutide. Side effects you log show how they move across your dose cycle, so you can see whether nausea returns after each Wegovy step. The weight report colours your weight line by dose through the gap.

Will you lose as much weight on Wegovy as on Mounjaro?

Our PubMed search on 26 October 2026 found no trial measuring weight outcomes after switching from Mounjaro to Wegovy.

SURMOUNT-5 found greater average weight loss with tirzepatide than semaglutide, with reductions of 20.2% and 13.7% respectively at 72 weeks (trial publication).

The trial randomised 751 adults with obesity and without type 2 diabetes to the maximum tolerated doses of each medicine (SURMOUNT-5). Tirzepatide doses were 10 mg or 15 mg; semaglutide doses were 1.7 mg or 2.4 mg (SURMOUNT-5).

Waist circumference fell by 18.4 cm with tirzepatide and 13.0 cm with semaglutide (SURMOUNT-5). Gastrointestinal events were the most common adverse events in the trial, mostly mild to moderate and mainly during escalation (trial publication).

Participants started their assigned treatment; SURMOUNT-5 did not test switching from established tirzepatide treatment to semaglutide (trial publication).

Why are people switching from Mounjaro to Wegovy in the UK?

A UK observational study found increased tirzepatide-to-semaglutide switching around the Mounjaro list-price rise (study publication). The study tracked when people switched, not why.

The NHS Business Services Authority reports these Mounjaro KwikPen list-price changes from September 2025 (price redetermination notice).

These are NHS list prices, not what a private pharmacy charges you. Current provider prices are in Pensday’s UK where-to-buy guides.

At one online provider with 1,033,522 self-paying adults, switching in September 2025 was 9.26 percentage points above its projected pre-September trend, before easing (study publication). The study did not report how the switchers’ weight changed (study publication).

Do side effects come back when switching from Mounjaro to Wegovy?

Wegovy can bring nausea, vomiting, diarrhoea and constipation during dose escalation; these are very common effects, affecting at least 1 in 10 people (Wegovy SmPC, section 4.8).

Over 68 weeks on Wegovy 2.4 mg, nausea affected 43.9% of patients against 16.1% on placebo, diarrhoea 29.7% (15.9%), vomiting 24.5% (6.3%) and constipation 24.2% (11.1%) (Wegovy SmPC, section 4.8). Most events were mild to moderate (Wegovy SmPC, section 4.8).

In the Wegovy trials, “The events were most frequently reported during dose escalation” (Wegovy SmPC, section 4.8).

The Wegovy dose climb lasts 16 weeks to reduce the likelihood of gastrointestinal symptoms (Wegovy SmPC, section 4.2).

For significant stomach symptoms, the SmPC allows the next step-up to be delayed, or the dose lowered to the previous step, until symptoms improve (Wegovy SmPC, section 4.2).

Can you switch from Mounjaro to Wegovy for maintenance?

We found no trial testing Wegovy maintenance after Mounjaro in our 26 October 2026 search; Wegovy’s labelled maintenance dose is 2.4 mg once weekly (Wegovy SmPC, section 4.2).

A switch for maintenance still starts Wegovy at 0.25 mg; the SmPC gives no conversion from an established Mounjaro dose (Wegovy SmPC, section 4.2).

For weight management in obesity, UK Wegovy can increase to 7.2 mg once weekly after at least 4 weeks on 2.4 mg, if needed (Wegovy SmPC, section 4.2). The UK 7.2 mg presentation is a single-dose pre-filled pen containing 7.2 mg in 0.75 mL (Wegovy 7.2 mg SmPC).

How does switching from Zepbound to Wegovy work in the US?

US Wegovy starts at 0.25 mg once weekly, and its switching instructions cover Wegovy tablets and injections rather than Zepbound (US Wegovy prescribing information, section 2). Zepbound’s prescribing information also gives no protocol for switching to or from another GLP‑1 medicine (US Zepbound prescribing information).

Check the Wegovy device as well as the prescribed dose. US single-dose pens come in each step from 0.25 mg to 2.4 mg, plus 7.2 mg, whereas the US FlexTouch instructions permit selecting only 2.4 mg (US Wegovy prescribing information and instructions for use).

If a Wegovy step is not tolerated, the US label says to “consider delaying dosage escalation for 4 weeks” (US Wegovy prescribing information, section 2).