Switching from Wegovy to Mounjaro

Last Updated: 2 October 2026

Mounjaro and Wegovy are both GLP-1 medications used for weight management in overweight and obese patients.

Mounjaro and Wegovy are both weekly injections used for weight management in adults with obesity or who are overweight.

However, they’re not the same medication, and no dose of Wegovy directly matches a dose of Mounjaro. Switching from Wegovy to Mounjaro needs a safe plan. It helps to know what to expect before you make the change.

Why switch from Wegovy to Mounjaro?

People switch from Wegovy to Mounjaro for many reasons, including:

• Greater weight loss results: Patients on Mounjaro lose, on average, more weight than those on Wegovy. SURMOUNT-5 compared the two medicines directly in one trial. People on Mounjaro lost an average of 20.2% of their body weight over 72 weeks. Those on Wegovy lost an average of 13.7% over the same time. The trial tested Wegovy doses up to 2.4mg, not the newer 7.2mg dose.
• Side effects: Wegovy side effects are similar to those of Mounjaro. But everyone responds to treatment in their own way. If you’re experiencing discomfort with Wegovy injections, you might want to try Mounjaro. You may find that you tolerate Mounjaro better, although switching does not guarantee this.

Finding the treatment and dose that works best for you can take time. We’ll help you and recommend adjustments where needed.

How do these treatments differ?

While both are weekly injections that help you lose weight, Wegovy (semaglutide) and Mounjaro (tirzepatide) are not the same. The main Wegovy vs Mounjaro difference is how many gut hormones each medicine copies.

Wegovy is a glucagon-like peptide-1 (GLP-1) agonist, which means it copies a gut hormone called GLP-1. Wegovy works by acting on the parts of the brain that control appetite. People taking it tend to feel fuller quicker, less hungry and have fewer food cravings.

Mounjaro also copies GLP-1, but it’s known as a ‘dual agonist’ because it copies a second gut hormone too. That second hormone is called glucose-dependent insulinotropic polypeptide (GIP). Mounjaro works on both hormone receptors, and both can act on the areas of the brain that control appetite.

The Mounjaro vs Wegovy differences go beyond hormones, Wegovy also has additional licences. One of which is to lower the risk of heart attack, stroke or death from heart disease in adults with existing heart disease. Mounjaro does not currently hold this licence, which may matter if you have a heart condition.

How to switch from Wegovy to Mounjaro safely

Switching weight loss medications needs medical supervision. To switch with Simple Online Pharmacy, you fill out an online consultation covering your medical history. Our clinicians will review it and contact you if they need any more information.

Mounjaro may make the contraceptive pill less effective. Wegovy is not expected to affect the pill in the same way. The Mounjaro prescribing information gives two options if you take the pill. You can move to a contraceptive that isn’t a pill. Alternatively, use condoms or another barrier method for four weeks after starting Mounjaro. You will need to do the same for four weeks after each dose increase.

To switch safely, you also need to leave the right gap between your last Wegovy injection and your first Mounjaro dose.   

What is the ‘washout period’ between Wegovy and Mounjaro?

We recommend a seven-day washout period when you switch. This is the gap between your last Wegovy injection and your first Mounjaro injection. If you take your last Wegovy dose on a Monday, you can then take your Mounjaro dose the following Monday.

Starting Mounjaro on the day your next Wegovy dose would have been due avoids doubling up. Taking Wegovy and Mounjaro in the same week could raise the risk of side effects. The Wegovy information leaflet also advises against using it with other GLP-1 medicines.

Wegovy does not leave your body within that week. Semaglutide, the medicine in Wegovy, clears slowly over several weeks. The Wegovy information leaflet advises stopping it at least two months before trying for a baby for this reason. Starting Mounjaro on a low dose helps limit side effects while the last of the Wegovy clears from your system. 

Some prescribers leave a longer gap of one to two weeks. A longer gap may suit people who had significant side effects on Wegovy.

Can I switch to a higher Mounjaro dose straight away?

You may be able to start Mounjaro at 5mg if you’re on Wegovy 2.4mg or 7.2mg. Whether you can depends on how well you’ve tolerated Wegovy and on your prescriber’s judgement. On any lower Wegovy dose, upon switching you start Mounjaro at 2.5mg.

Your Wegovy dose	Mounjaro starting dose
0.25mg, 0.5mg, 1mg or 1.7mg	2.5mg
2.4mg or 7.2mg	5mg

This table shows our switching policy, not a licensed dose conversion. The licensed Mounjaro starting dose is 2.5mg.

If you have had side effects on Wegovy, your prescriber may start you on the lowest dose of 2.5mg instead. No set dose match exists between the two medicines because they act on different gut hormones. You can speak with our clinical team if you are unsure which dose is right for you.

The Mounjaro prescribing information sets a minimum of four weeks on each dose. Doses then rise in 2.5mg steps, up to the highest dose of 15mg. The recommended maintenance dose options are 5mg, 10mg and 15mg.

Under our policy, you can move up to the next dose after at least 4 weeks on your current strength.

Can I switch back to Wegovy?

Yes, you can return to Wegovy after switching to Mounjaro. However, we may suggest giving Wegovy more time first. Some patients may want to return to Mounjaro after switching from Mounjaro to Wegovy. 

One reason to switch back is that Wegovy may not work as well for you as Mounjaro did. Mounjaro is a dual-agonist medication. It targets both GLP-1 and GIP hormones, meaning it can be more effective. Wegovy only targets GLP-1 receptors. This means you might feel a little hungrier than usual at first after moving to Wegovy. This is normal as your body adapts.

If you’re not experiencing significant side effects, our clinicians would advise continuing with Wegovy. If you’re not feeling full or satisfied enough after meals, a higher dose may help. You can move up to the next Wegovy dose once you’ve been on your current strength for at least 4 weeks.

If you would still like to switch back to Mounjaro, you can call our Patient Care Team, who can advise on the safest approach.

Will I get side effects after switching?

You may get side effects after switching, because they tend to be worse when you start a treatment and when you increase your dose. Overall, the side effects of Wegovy and Mounjaro are similar.

Mild digestive symptoms are common, especially in the first few weeks and after each dose increase. Common Mounjaro side effects you may notice include:

• Feeling sick or vomiting
• Reduced appetite
• Bloating or stomach pain
• Loose stools or mild constipation
• Tiredness

Digestive side effects usually ease over time. The NHS advises speaking to a pharmacist or doctor if side effects bother you or don’t go away. If symptoms feel stronger than expected, staying on the same dose for longer may help.

How will switching affect my progress?

Mounjaro led to more weight loss than Wegovy on average in SURMOUNT-5. Switching may help your weight loss in the long term. 

However, in the first few weeks after switching, you may feel hungrier than usual. Your weight may stay the same or increase slightly while you’re on the lower Mounjaro doses. This does not mean the medication isn’t working for you. Your body is adjusting to a new medicine at a lower starting dose. You may feel less hungry as your Mounjaro dose goes up.

Weight loss progress isn’t always steady, and plateaus are a normal part of treatment.

Do lifestyle changes matter alongside a weight loss injection? 

Both Wegovy and Mounjaro are licensed for use alongside healthy eating and more physical activity, not instead of them.

Weight loss treatment takes time, and the right medicine is one you respond well to and can stay on.

If you felt little or no effect on Wegovy, switching to Mounjaro may give you a better chance of reaching your goals. But plan the switch carefully to get the best results.

We’re here for you through every step of your weight loss journey. If you need any support, you can call our Patient Care Team for advice.

When should I see a doctor?

Most side effects after switching are mild or moderate, but a few need urgent medical help.

Contact our clinical team if you have:

• Feeling sick, being sick, diarrhoea or constipation that you can still manage
• Heartburn, reflux or changes in your appetite
• Questions about your Mounjaro dose or when to move up

Speak to your GP or call NHS 111 the same day if you have:

• Yellowing of your skin or the whites of your eyes
• Severe pain in the upper right side of your stomach
• Vomiting or diarrhoea that stops you keeping fluids down for more than six hours
• Low blood sugar signs, like dizziness or confusion, if you also take insulin or gliclazide 

Call 999 or go to A&E, and stop Mounjaro, if you notice any of the following:

• Severe stomach pain that spreads to your back and does not go away
• Swelling of your face, lips, tongue or throat, or difficulty breathing
• Signs of severe dehydration after repeated vomiting or diarrhoea
• Blurring or loss of vision in one or both eyes. This may be a sign of non-arteritic anterior ischemic optic neuropathy (NAION).

Whatever the cause, if you have thoughts of harming yourself, go to A&E and ask for the CRISIS team.

Key takeaways

• A seven-day gap is the usual washout period. Take your first Mounjaro dose seven days after your last Wegovy injection, on the day your next Wegovy dose would have been due.
• Your Mounjaro starting dose depends on your Wegovy dose. You may start at 5mg from Wegovy 2.4mg or 7.2mg, depending on your tolerance and your prescriber’s judgement. On lower Wegovy doses, you start at 2.5mg.
• Check your contraception: if you take the pill, use condoms as well for four weeks after starting Mounjaro and after each dose increase.
• Side effects are common at first but usually improve. Mild nausea, bloating or changes in appetite can happen when switching, especially in the first few weeks. These symptoms normally settle as your body gets used to Mounjaro.
• A temporary pause in progress is normal. Your weight might stay the same or even increase slightly. Appetite control may return as you move up through the Mounjaro doses.

References

Tirzepatide as Compared with Semaglutide for the Treatment of Obesity, New England Journal of Medicine, 2025 [Accessed 10 September 2026]

Mounjaro KwikPen solution for injection in pre-filled pen: Summary of Product Characteristics, electronic medicines compendium, 2026 [Accessed 10 September 2026]

Wegovy 2.4 mg, FlexTouch solution for injection in pre-filled pen: Summary of Product Characteristics, electronic medicines compendium, 2026 [Accessed 10 September 2026]

Switching between weight-loss medications, The Pharmaceutical Journal, 2026 [Accessed 10 September 2026]

Tirzepatide: a medicine to manage type 2 diabetes and treat obesity, NHS, 2026 [Accessed 10 September 2026}

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