22 August, 2025 | Jabbar Ali - MPharm
If you're taking weight loss medication and thinking about switching, whether that's moving from Mounjaro to Wegovy, Wegovy to Mounjaro, or between an injection and a tablet like Orlistat - you're in good company. Cost, side effects, supply, plateaued results and simple personal preference are all common, completely valid reasons to consider a change.
The good news is that switching is a well-understood process when it's done with the right support. This guide walks through the principles that apply whichever direction you're moving: the washout period, your likely starting dose, what to expect during the transition, and how to switch safely.
Yes, many people can switch between weight loss medications if supply problems, side effects, cost, plateaued results, or personal choice make a different treatment a better fit. There are no official head-to-head trials, so decisions must always be made on an individual basis. A healthcare professional will advise you on when to stop one medication and start the other, and whether switching is appropriate for your circumstances.
There's rarely just one reason, it usually comes down to a mix of the following:
Whatever's brought you here, it's a normal part of finding the weight loss treatment that works best for you.
A washout period is a planned gap between stopping one medication and starting another, allowing the first treatment to begin clearing your system before the new one starts working. For switches between GLP-1 medications - for example, between Mounjaro and Wegovy in either direction - the standard washout period is typically 7 days. This short pause reduces the risk of overlapping side effects, such as nausea or bloating, from both medications acting at once. If you experienced severe side effects on your previous treatment, your prescriber may recommend a longer gap, sometimes up to four weeks.
In practice, this means: take your last dose of your current medication as scheduled, then wait at least seven full days before your first dose of the new one. For example, if your last dose is on a Friday, your first dose of the new medication would typically be the following Friday.
Switches involving Orlistat work differently, since it's a tablet that works in the gut rather than an injection that affects appetite hormones - your prescriber can advise on the right transition timing if you're moving to or from Orlistat.
After a 7-day washout, most patients restart at Wegovy's lowest dose (0.25mg weekly), regardless of their previous Mounjaro dose, then follow the standard titration schedule. Mounjaro works on both GLP-1 and GIP receptors, while Wegovy works on GLP-1 alone, so some patients notice a difference in how appetite suppression feels during the first few weeks.
The same 7-day washout applies in this direction. Patients restart at Mounjaro's lowest dose (2.5mg weekly) regardless of their previous Wegovy dose, then titrate up as usual. This direction is sometimes considered when a patient has plateaued on Wegovy, since Mounjaro's dual mechanism can produce stronger results for some people - see our Mounjaro vs Wegovy comparison for more detail.
Because Orlistat works in the gut rather than on appetite hormones, there's no washout period required when switching to or from a GLP-1 injection in the way there is between two GLP-1 medications. You can typically stop one and start the other on your prescriber's guidance, though they may stagger the transition slightly to help you adjust to the change in side effect profile.
Always speak to your GP, obesity specialist, or pharmacy prescriber before changing treatments.
Have a 7-day washout period when switching between GLP-1 medications, as covered above.If side effects were severe, a longer break may be recommended.
Most patients start at the lowest dose of their new medication and follow the usual titration schedule from there, as explained above. Your prescriber will confirm the right starting point for you individually based on your treatment history.
| Mounjaro Dose | Guide for Wegovy Switch |
|---|---|
| 2.5mg | 0.5mg |
| 5mg | 0.5mg |
| 7.5mg | 1mg |
| 10mg | 1mg |
| 12.5mg | 1.7mg |
| 15mg | 2.4mg |
This chart is only a general guide. Your prescriber may adjust your starting dose for safety.
“Switching treatment is something we help patients with regularly. The most common misunderstanding is that you can swap one medication for another at the same strength. In most cases you'll restart at the lowest dose and build up again, so it's worth expecting the first few weeks to feel different. Please don't make the change on your own. A prescriber can check if the switch is right for you, plan the timing and support you through it.”
Omar El-Gohary, Superintendent Pharmacist, IQ Doctor
GLP-1 medications including Wegovy are supported for long-term obesity management under NICE guidelines. Treatment usually includes support with:
You can access Wegovy through NHS Tier 3 weight management services or privately.
Switching between weight loss medications is a safe, recognised process when managed properly, whichever direction you're moving in. The most important steps when switching are:
Never switch between treatments without consulting a healthcare professional.
If you're considering switching weight loss medications, our clinical team can help you understand whether a change is suitable for you and what the transition may involve.
Not necessarily. Different medications can produce different results, and individual response varies significantly from person to person. Many patients achieve excellent results on more than one treatment, but it's worth setting realistic expectations rather than assuming an identical outcome.
In most cases, yes - switching back is generally possible under medical supervision, following the same washout principles in reverse. Discuss this with your prescriber if you're considering a switch but want to keep this option open.
It's unlikely to be significant. Your previous medication's effects typically continue for several days after your last dose, and the washout period is short enough that any appetite increase tends to be mild and temporary, usually resolving once the new treatment starts working.
Yes. Switching from one prescription-only medication to another always requires a new clinical assessment, even if you're already an existing patient. This ensures your new treatment is suitable for you and allows your prescriber to confirm the right starting dose. You can begin this process through IQ Doctor's online consultation.
This page has been written by a registered UK pharmacist and reviewed by our clinical team to ensure it is accurate, clear and reflects current clinical guidance.
Last medically reviewed: 22 August, 2025
Last updated: 13 October, 2026