Switching from Wegovy to Mounjaro

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

However, they’re not the same medication and there is no direct dose equivalent between the two. So, if you’re thinking of switching from Wegovy to Mounjaro, it is important to follow a safe plan and understand what to expect before making the change.

Here’s how to do it safely, what side effects to expect, and how switching to Mounjaro may affect your progress.

Why Switch from Wegovy to Mounjaro?

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

• Higher weight loss results: Patients on Mounjaro lose on average more weight than those on Wegovy. In clinical trials, Mounjaro patients lost up to 22.5% of their starting body weight after 72 weeks. On Wegovy, people lost up to 17% of their starting weight over 68 weeks.
• Side effects: The side effects of Wegovy and Mounjaro are very similar. But everyone responds to treatment differently. If you’re experiencing discomfort on Wegovy, you might want to try Mounjaro. You may find side effects more manageable.

Each person responds to each weight loss medication differently. Some people might find the appetite-suppressing effects of one medication greater than the other. Or that side effects are more manageable on one treatment compared to the other.

Finding the treatment and dose that works best for you can take time. Your provider will help you and make 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.

Wegovy is a glucagon-like peptide 1 (GLP-1) agonist. Wegovy works by mimicking the hormone GLP-1, which regulates appetite and digestion. This slows down the rate at which food leaves the stomach. This helps you feel fuller quicker and for longer.

Mounjaro is also a GLP-1 agonist. However, it’s a “dual agonist” because it also mimics the hormone glucose-dependent insulinotropic polypeptide (GIP). This hormone also regulates appetite and digestion.

For more information on the differences between Mounjaro vs Wegovy, head to this article.

How to Switch from Wegovy to Mounjaro Safely

Switching weight loss medications needs to be done under medical supervision. To switch with Simple, you just need to fill in an assessment form online. Our clinicians will review it and contact you if they need any more information.

To switch safely, you also need to give your body enough time to “wash out” the old medicine before starting the new one.

What is the ‘Washout Period’ Between Wegovy and Mounjaro?

A short break – or “washout period” – between treatments helps reduce side effects and prevents too much appetite suppression at once.

Patients using Wegovy should take a one week break before starting Mounjaro. So, if you take your last Wegovy dose on a Monday, you can then take your Mounjaro dose the following Monday.

This guidance is based on how long it takes Wegovy to leave your system. The higher the dose, the longer the medicine remains active.

Can I Switch to a Higher Mounjaro Dose Straight Away?

No. When you switch, you should start Mounjaro on the lowest dose (2.5 mg) and increase your dose gradually. This is the best approach for managing side effects.

Even if you were on the highest Wegovy dose (2.4 mg), you cannot jump straight into a high Mounjaro dose.

Like Wegovy, you will stay on each dose of Mounjaro for at least four weeks, until you reach a maintenance dose.

Can I Switch Back to Mounjaro After Switching From Mounjaro to Wegovy?

Some patients may want to return to Mounjaro after switching from Mounjaro to Wegovy. This may be, for example, if they find they’re not responding to Wegovy as much as Mounjaro.

It can take time to find the right treatment and dose for your body. You might notice feeling a little hungrier than usual at first, 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, you may be able to increase your dose after you’ve taken four consecutive doses of your current strength.

If you would still like to switch back to Mounjaro, your prescriber can advise on the safest approach. If you’re a patient with Simple Online Pharmacy, call us on 0141 774 5023.

Will I Get Side Effects After Switching?

The side effects of Wegovy and Mounjaro are very similar. They tend to be worse when you start treatment and when you increase your dose. So you may experience side effects after switching.

Some people notice mild digestive symptoms, especially in the first two to four weeks. Common Mounjaro side effects include:

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

These usually settle as your body adapts. If symptoms feel stronger than expected, staying on the same dose for longer can help.

Serious side effects are rare, but if you experience severe stomach pain, repeated vomiting or dehydration, seek medical help.

How Will Switching Affect My Progress?

Some patients experience better appetite control on Mounjaro. So switching may support your weight loss progress in the long term.

However, during the washout period, you may feel hungrier than usual. Your weight may stay the same or increase slightly. This does not mean the medication isn’t working for you. Your body is simply adjusting. You’ll likely feel more appetite suppression as you move through the dose increases.

Remember that weight loss progress isn’t always linear. Changes and plateaus are all normal.

GLP-1s Are a Tool and Lifestyle Changes are Key

Weight loss treatment is a journey. What matters most is finding a medicine that you respond to, can tolerate 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 the switch needs to be done carefully for the best results.

We’re here for you through every step of your weight loss journey. So, if you need any support, call us on 0141 774 5023.

Key Takeaways

• A One-Week “Washout Period” Is Essential: You need a one-week gap between stopping Wegovy and starting Mounjaro to avoid strong side effects.
• There Is No Equivalent Dose Between the Two Medicines: Wegovy and Mounjaro weight loss injections work differently. So there are no equivalent doses. This means switching safely is not about “matching” doses, but about starting at the right level for your body.
• Patients Should Start Mounjaro at 2.5 mg: Even if you were on a high dose of Wegovy, you should start on the lowest dose. It lets your body adjust and reduces the chance of nausea or an upset stomach.
• 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. Once you move through the Mounjaro dose steps, appetite control usually returns and progress picks up.

References

A Practical Guide to Using Medicines to Manage Overweight and Obesity – Prescribing, reviewing and stopping tirzepatide, 2025. National Institute for Health and Care Excellence (NICE) [online]. Available from: https://www.nice.org.uk/guidance/ta1026/resources/a-practical-guide-to-using-medicines-to-manage-overweight-and-obesity-15299628589/chapter/prescribing-reviewing-and-stopping-tirzepatide.

Wilding, J.P.H., Batterham, R.L. and Calanna, S. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine, [online] 384(11), pp.989–1002. doi:https://doi.org/10.1056/NEJMoa2032183.

Jastreboff, A.M., Aronne, L.J., Ahmad, N.N., Wharton, S., Connery, L., Alves, B., Kiyosue, A., Zhang, S., Liu, B., Bunck, M.C. and Stefanski, A. (2022). Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine, [online] 387(3), pp.205–216. doi:https://doi.org/10.1056/nejmoa2206038.

Four-dose Mounjaro “KwikPen” approved by MHRA for diabetes and weight management, 2024. GOV.UK. [online]. Available from: https://www.gov.uk/government/news/four-dose-mounjaro-kwikpen-approved-by-mhra-for-diabetes-and-weight-management.

Kommu, S., Whitfield, P., 2024. Semaglutide. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. [online]. Bookshelf ID: NBK603723. Available from: https://www.ncbi.nlm.nih.gov/books/NBK603723/.

Mounjaro (how Mounjaro works), 2025. Mounjaro. [online]. Available from: https://mounjaro.lilly.com/hcp/how-mounjaro-works.

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