Switching from Mounjaro to Wegovy - How to do it
Thinking about moving from Mounjaro to Wegovy can feel like changing gears mid-journey: doable, but smoother with a clear plan and realistic expectations. You’re not starting from scratch, but semaglutide (Wegovy) and tirzepatide (Mounjaro) act a little differently in the body, so the switch should be thoughtful and paced.
This guide explains how to plan the change, what doses to use, and how to make the first few weeks as comfortable and effective as possible, based on trusted UK prescribing information and practical patient advice.
Wegovy (semaglutide) and Mounjaro (tirzepatide) are once-weekly injectable medicines that help with weight loss by acting on gut hormone pathways that reduce appetite and support healthier eating patterns. Tirzepatide (the active in Mounjaro) works on both GLP-1 and GIP receptors, while semaglutide (Wegovy) targets GLP-1 alone; the switch is safe when done with the right timing and dosing steps. This matters because moving too quickly can worsen stomach side effects and make the transition harder than it needs to be.
How the switch works, step by step
Switching usually involves a short pause, then restarting at the beginning of Wegovy’s dose ladder to let your gut adapt gradually.
- Take the last Mounjaro injection as scheduled, then wait 4–5 weeks before starting Wegovy. This longer break allows Mounjaro to fully clear from your system, helping to reduce the risk of overlapping side effects and giving your body time to adjust before beginning the new treatment.
- Start Wegovy at 0.25mg once weekly, then step up every 4 weeks as tolerated: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg (maintenance).
- Keep the same injection day each week to maintain steady levels and reduce side effects.
Wegovy’s official UK product information recommends this 16-week dose escalation to lower the chance of nausea, reflux, and other GI symptoms during the transition. If side effects bite, your prescriber may pause at a lower step for longer before moving up.
What to expect in the first month
The first 2–4 weeks after switching are about settling into semaglutide at a gentle starting dose, not chasing fast results. Appetite control may feel slightly different from Mounjaro because the medicines act via partly different hormone signals, but most people start noticing steadier hunger and fewer cravings as the Wegovy dose increases through the ladder.
One UK user described that after two weeks on the starter Wegovy pen, snacking urges eased and portion sizes felt naturally smaller-helpful, but milder than on higher doses, which is expected early on. Staying patient with the titration is key.
Dosing details at a glance
- Wegovy start and steps: 0.25mg weekly for 4 weeks, then 0.5mg, 1mg, 1.7mg, and 2.4mg maintenance, each step usually lasting 4 weeks.
- Mounjaro (for context): typically begins at 2.5mg weekly, increasing by 2.5mg every 4 weeks (e.g., 5mg, 7.5mg, up to 15mg).
- Do not "convert" doses directly between Mounjaro and Wegovy; they’re different medicines, so always follow Wegovy’s own titration schedule when you switch.
Making the transition easier
The gentler the start, the better your gut tends to feel. A few simple habits help the body adjust:
- Eat slowly and stop at "comfortably full" to avoid nausea.
- Prioritise lean protein, vegetables, and fibre; keep fizzy drinks and heavy, fatty meals modest.
- Sip water through the day rather than large drinks at once.
- Keep a consistent injection day and rotate injection sites to reduce irritation.
If nausea, bloating, or reflux become troublesome, staying an extra four weeks at the current dose (before stepping up) is a common and sensible tweak your prescriber may recommend.
Expert insight
"Switching between GLP-1 medicines isn’t about finding an identical replacement-it’s about giving your body time to adjust to a slightly different mechanism. By following the slower dose escalation and listening to your body’s feedback, you can maintain progress while reducing the risk of side effects." - Alessandro Grenci, Superintendent Pharmacist
A real-world perspective
People often worry they’ll lose progress when changing medicines. In practice, many find the weekly rhythm familiar, and once they reach the mid-range Wegovy doses (1mg to 1.7mg), appetite control feels more recognisable again. One UK user said their appetite dipped noticeably after two weeks on Wegovy, with more significant changes as they climbed to the 1mg and 1.7mg steps-lining up with the product’s gradual escalation plan.
Risks and considerations
The most common transition issues are gastrointestinal-nausea, indigestion, constipation or diarrhoea-usually improved by slow titration and smaller meals. Very rarely, GLP-1 medicines can affect gallbladder health; seek medical help for persistent severe abdominal pain, especially with fever or jaundice.
When to contact your prescriber
- Persistent vomiting or dehydration, or symptoms that don’t settle with slower titration.
- Concerns about medicines whose absorption may be affected—such as certain antibiotics, oral contraceptives, thyroid hormone tablets, immunosuppressants, or anticoagulants - for which dose adjustments might be required.
- If you miss a dose: Wegovy allows some flexibility, but follow the patient leaflet or prescriber advice for timing your next injection.
Key Takeaways
- Plan a four or five-week gap after your last Mounjaro dose, then start Wegovy at 0.25mg weekly.
- Step up every 4 weeks (0.25 → 0.5 → 1 → 1.7 → 2.4mg) unless side effects mean you need longer at a dose.
- Don’t convert doses directly between Mounjaro and Wegovy; follow Wegovy’s own schedule.
- Expect gentler effects at first; appetite control typically strengthens as doses increase.
- If side effects persist, pause dose increases and speak with your prescriber.
You’re not starting over-you’re adjusting your tools; with a steady plan and a bit of patience, the switch can be smooth and effective.
