Can I switch weight loss treatment?

Wegovy and Mounjaro are similar treatments, but the doses are different – and if you want to switch between these two injections, the way you do it will depend on what dose of medication you’re currently using, and how long it’s been since your last injected dose.

At time of writing, there was no firmly-established, specific advice for switching between Wegovy and Mounjaro available from the manufacturers of these treatments, or NICE.

But the clinical team at Treated have developed specific switching guidance based on evidence from available research.

In any case, you should always check with your clinician before making the switch. Their recommendations may differ, depending on your individual response to GLP-1 treatment and your current progress.

It’s also important to keep practising the healthy habits you’ve been developing – such as eating healthily and exercising regularly – to help your new treatment work at its best.

Switching from Mounjaro to Wegovy

If you want to change from Mounjaro to Wegovy, and the gap between your most recent Mounjaro dose and your upcoming Wegovy dose is less than two weeks, our recommendation is to switch to:

• the 0.25mg dose of Wegovy if your last Mounjaro dose was 2.5mg
• the 0.5mg dose of Wegovy if your last Mounjaro dose was 5mg
• the 1mg dose of Wegovy if your last Mounjaro dose was either 7.5mg or 10mg
• the 1.7mg dose of Wegovy if your last Mounjaro dose was either 12.5mg or 15mg

After four weeks at your new Wegovy dose, you can then move up to the next dose if your treatment is going well and you aren’t experiencing significant side effects.

If you plan to change from Mounjaro to Wegovy, and the gap between your most recent Mounjaro dose and your upcoming Wegovy dose is more than two weeks but less than four weeks, our recommendation is to drop an extra dose, by switching to:

• the 0.25mg dose of Wegovy if your last Mounjaro dose was 2.5mg or 5mg
• the 0.5mg dose of Wegovy if your last Mounjaro dose was 7.5mg or 10mg
• the 1mg dose of Wegovy if your last Mounjaro dose was either 12.5mg or 15mg

Again, after four weeks at your new Wegovy dose, you’ve got the option to move up a dose if your treatment is going well.

If you want to change from Mounjaro to Wegovy, and the gap between your most recent Mounjaro dose and your upcoming Wegovy dose is more than four weeks, our recommendation is to start at the lowest of Wegovy (0.25mg) regardless of which dose of Mounjaro you most recently used.

Switching from Wegovy to Mounjaro

If you want to change from Wegovy to Mounjaro, our recommendation is to:

• wait until it’s been at least 6 weeks since your last injected dose of Wegovy
• then start at the lowest dose of Mounjaro (2.5mg)

You can then escalate through the doses as normal, provided the medication is working well for you.

Injectable weight loss treatments are usually ‘GLP-1 receptor agonists’. This is a type of drug that was originally licensed for type-2 diabetes, though there are now GLP-1 receptor agonists formulated specifically for weight loss, like Saxenda and Wegovy. GLP-1 agonists work in your brain to make you feel fuller and less hungry.

Mounjaro is another injectable medication, but it contains a different active ingredient called tirzepatide. It works in a similar way to Saxenda and Wegovy, but its action is a bit more complex because it targets both GLP-1 and GIP receptors.

Oral weight loss treatments, however, work in slightly different ways. There are two different types of oral medication licensed for weight loss: orlistat (brand names Alli and Xenical) and Mysimba (which uses the active ingredients bupropion and naltrexone).

Orlistat works quite differently from injectable weight loss treatments, in that its primary mode of action isn’t to help regulate your food intake by making you feel fuller or less hungry. Instead it works in your digestive system to reduce the amount of calories you take in from the food you eat. It binds to the enzymes that break down fats in your body stopping it from being absorbed. So it’s not the best weight loss drug if you’re on a low fat diet. But, you might want to switch from an injectable treatment to orlistat if you’ve been experiencing certain side effects, like insomnia, from your treatment.

Mysimba, on the other hand, works in a more similar way to injectable weight loss treatments. This is because it works on parts of your brain responsible for cravings. So it helps you lose weight by making food less appealing to you, therefore making you more likely to be in a calorie deficit. It’s even more effective when used alongside weight loss management counselling.

This makes Mysimba a more ‘natural’ treatment to switch to from injectable treatments, as it won’t feel quite so much of a change as switching to a treatment with a completely different mode of action. This kind of switch could be ideal for you if you’re finding using injectable treatment difficult, or if it becomes unavailable.

When switching to Mysimba, you’ll probably be advised to start at the lowest dose (one tablet a day), which you’ll then need to gradually increase to four tablets a day after three weeks of taking it. This might feel like a bit of a step backwards if you’re already on a higher dose of another treatment, but it’s important for your safety to gradually build up to the higher doses of a new treatment so that your body can get used to it.

When switching from tablets to injections, you’ll still need to consider the way the drug works in your body, as well as the fact that you’ll need to start again at a lower dose. But another thing you’ll also need to consider is the method of administration. Some people don’t feel comfortable using needles, so you’ll need to make sure that you’re confident and able to use this treatment before you start. 

Using an injectable treatment can feel a little less convenient than tablets or capsules. But once you’re used to it you might actually find that these treatments are easier to stick to. This is because tablet treatments usually need to be taken multiple times a day, and with orlistat you’ll need to make sure you sync your doses with your meal-times. Whereas you only need to use liraglutide injections (like Nevolat or Plaobes) once a day, and Wegovy and Mounjaro even less (once a week). This means that with injections you’ll only need to set aside – at most – one time a day to use your treatment. And the rest of your day is for you.

When switching oral weight loss treatments, such as orlistat to Mysimba (or vice-versa), the main things you’ll need to consider are your dosing schedules and diet. Orlistat, for example, should be taken three times a day around each of your main meals. Mysimba on the other hand has a slightly more complex dosing schedule, which involves taking one tablet a day in your first week, leading up to four tablets spread across your day by week four.

Another thing to consider is how the drugs work and, as a result, the effect they might have on your diet and lifestyle. Orlistat, for instance, works best on dietary fat from the food you eat, and it needs to be taken alongside meals for you to get the best results from it. So if you’ve not been eating three meals a day then you’ll likely be advised to start doing so when you start taking orlistat.

On the other hand, if you switch from orlistat to Mysimba you might need to get used to having fewer food cravings, and so perhaps eating less food than you’re used to.

Switching from one injection treatment to another for your weight loss is arguably the easiest of these changes you can make. This is because both of these licensed injectable treatments (Wegovy and Saxenda) use the same type of drug as their active ingredient. This means that they’ll both work in largely the same way in your body.

They’re not exactly the same, though – Saxenda uses Liraglutide and Wegovy uses Semaglutide. The main differences between them are that Wegovy lasts longer in the body (and so only needs to be taken once a week), and that some initial research has shown Wegovy to be more effective.

Wegovy uses the same active ingredient as the diabetes medication, Ozempic – which can also be prescribed as an ‘off-label’ treatment for weight loss. ‘Off-label’ simply means that the treatment has been prescribed for something outside its medicinal licence, when a clinician decides it’s safe and suitable to do so.

So if you’re taking Ozempic as an off-label treatment, switching to Wegovy could be even easier. You might still have to follow the titration process of gradually increasing your dose. This is because Wegovy is available in higher doses than Ozempic, so you’ll need to gradually increase to this higher dose to make sure it’s still right for you.