Mounjaro vs Ozempic

Mounjaro and Ozempic are two popular injectable medications prescribed to support weight loss and manage diabetes. Both are glucagon-like peptide 1 (GLP-1) receptor agonists, meaning they work by reducing appetite and helping regulate blood sugar levels.

If you’re not sure which one is right for you, this guide will break down the differences between Mounjaro and Ozempic – from side effects, cost, dosages, and more. By the end, you’ll have all the information you need to start your weight loss journey doubt-free.

Mounjaro and Ozempic are both injectable medications that contain a glucagon-like peptide 1 (GLP-1) receptor agonist. Mounjaro’s main active ingredient is tirzepatide, and Ozempic’s main active ingredient is semaglutide.

Ozempic is licensed in the UK to treat type 2 diabetes. Mounjaro is licensed in the UK to treat both weight loss and type 2 diabetes. Both medications are most effective when taken alongside a balanced healthy diet and exercise routine.

Mounjaro and Ozempic both contain GLP-1 (glucagon-like peptide 1) receptor agonists, however, they each contain different active ingredients. Mounjaro contains tirzepatide, and Ozempic contains semaglutide.

Both Mounjaro and Ozempic are able to help with weight loss, according to some studies. However, only Mounjaro is licensed to be used as a treatment for weight loss in the UK, whereas Ozempic is not.

A range of clinical studies have assessed the effectiveness of tirzepatide (Mounjaro) and semaglutide (Ozempic). Wegovy also contains the active ingredient semaglutide but is approved for weight loss in the UK. Overall, tirzepatide (Mounjaro) has been found to be more effective for weight loss than semaglutide.

Effectiveness of Mounjaro (tirzepatide):

• 96.3% of people lose at least 5% of starting weight on the highest maintenance dose of 15mg after 72 weeks
• 62.9% of people lose over 20% of their starting weight on the highest maintenance dose of 15mg after 72 weeks

Effectiveness of Wegovy (semaglutide, the same active ingredient as Ozempic, but licensed for weight loss at a higher maximum maintenance dose):

• 83.5% of people lose at least 5% of starting weight on the highest maintenance dose of 2.4mg after 68 weeks
• 30.2% of people lose over 20% of starting weight on the highest maintenance dose of 2.4mg after 68 weeks

Although the way of taking Mounjaro and Ozempic is similar, they do not follow the same dosages.

Ozempic dosages are tailored to treat diabetes, whereas Mounjaro dosages are more targeted to treating weight loss.

The side effects of Mounjaro and Ozempic are similar, this is because they both contain medication from the same drug group (GLP-1).

How long do side effects last when taking Mounjaro or Ozempic?

How long side effects last varies from person to person. You’re most likely to experience side effects with weight loss treatments when you start the treatment, and when you increase your dose during treatment.

Mounjaro side effects which are mild typically last between a few days to a couple of weeks. More severe side effects tend to take longer to go away, you should discuss any severe side effects which become bothersome with your doctor.

Ozempic side effects are typically associated with diabetes rather than weight loss. Clinical studies have found that diabetes patients experienced side effects mainly between a few days to a few weeks. However, this can vary from person to person.

There is more information about the potential side effects of Mounjaro and Ozempic in the patient information leaflets which you can find with the medications.

What should I do if I get side effects?

Common side effects of Mounjaro and Ozempic should improve once your body gets used to the medication.

To manage common side effects at home, we recommend:

• Staying hydrated: Keeping hydrated and sipping cold drinks regularly should ease symptoms of sickness or nausea and dehydration.
• Avoiding alcohol: Alcohol will make you more dehydrated and increase side effects.
• Making changes to your diet and exercise routine: Ozempic and Mounjaro are most effective and safe when you follow a well-balanced diet and exercise plan. Speak with your doctor for personalised advice on fitness and nutrition.
• Avoiding fatty or greasy foods: Fatty and/or greasy foods can increase symptoms of sickness or nausea due to their richness. We recommend eating small, frequent, bland meals including rice, toast and crackers.
• Avoiding citrus, spicy and acidic foods: Sometimes when taking Ozempic or Mounjaro, you may have increased symptoms of acid reflux and heartburn. Avoiding citrus, spicy or acidic foods can minimise these symptoms.

Ozempic is not licensed to be sold as a weight loss treatment in the UK and is not available on the NHS for this purpose. So it is likely you would have to pay full price for the medication. If it’s prescribed for managing diabetes, it can cost just the standard prescription fee if you normally have to pay for your prescription, or it can be free.

Wegovy contains the same active ingredient as Ozempic, although, unlike Ozempic, it’s available and approved to purchase via prescription for weight loss in the UK. It also comes in higher doses for weight loss.

Yes, you can switch from Ozempic to Mounjaro to help you achieve better weight loss results, as long as you’re taking Ozempic for weight loss (not diabetes). If you’re eligible for Ozempic, Mounjaro is likely to be a safe treatment for you as well, but you should always check with a doctor first. To safely switch from Ozempic to Mounjaro, you need to:

1. Stop taking Ozempic after your last dose is finished.
2. Wait 7 days before starting Mounjaro. You need to leave this break between treatments to reduce the chance of side effects.
3. Start taking Mounjaro after 7 days. Your doctor will advise you on which Mounjaro dose you can start on, depending on what Ozempic dose you were taking.

The maximum starting dose after switching treatments with ZAVA is Mounjaro 5mg.

Do not switch medications without first consulting a doctor. Your doctor will give you specific instructions on how to switch safely, and guide you through the process.

Is it safe to switch?

Yes, if you are taking Ozempic for weight loss, it is usually safe to switch to Mounjaro. It may not be safe if you have severe side effects, in which case you should discuss this with your doctor first.

What should I expect when I switch from Ozempic to Mounjaro?

Regardless of the dosage you were taking on Ozempic, if you switch with ZAVA, Mounjaro will be started on a lower dose of either 2.5mg or 5mg, decided by your doctor. This is gradually increased (titrated) to a dosage which works for you and your weight loss journey, just like you did with Ozempic. You may find that you experience side effects when starting Mounjaro as your body adjusts to the new medication. If you experience ongoing, severe and bothersome side effects, you should discuss them with your doctor.

Please note: even if you are taking 1mg of Ozempic, this does not mean you would start on 7.5mg of Mounjaro. You still need to start on a lower dose chosen by your doctor to reduce the chance of serious side effects.

Who can help me switch?

If you’re currently taking Ozempic for diabetes, your GP or NHS diabetes specialist is the only one who can swap you over to Mounjaro. This will be based on your weight and how well Ozempic is controlling your diabetes symptoms.

If you’ve been taking Ozempic off-label as a weight loss treatment, you can switch with the help of a weight loss management service, including ZAVA. Either way, if you have diabetes, the prescribing doctor will need to know what diabetes medication you take and you’ll need to speak to your GP, as the doses of some of your other medications may need to be changed.

If you’re currently using Ozempic off-label as a weight loss medication (not a diabetes treatment) but are considering starting your weight loss journey with an approved weight loss treatment in the UK, Mounjaro may be an effective option.

If you’re comfortable using Ozempic and are apprehensive about adjusting to a different active ingredient, Wegovy uses the same active ingredient as Ozempic but in higher doses which specifically target weight loss.

If you are uncertain about self-injecting weight loss medication, there are oral tablet form alternatives such as:

• alli
• Xenical
• orlistat

When deciding on a weight loss treatment that is safe, approved and right for you, it can take some time to find the right choice. The differences between all treatments may seem quite small at first in terms of how they work, side effects, and how to take them. However, based on studies of overall effectiveness, Mounjaro is the most effective.

A doctor should be able to help you find a treatment that aligns best with your personal health needs, particularly if you have previously been taking Ozempic for the treatment of diabetes. If you have any queries or concerns about your weight loss journey, our doctors are here to help answer your questions.

Subcutaneously administered tirzepatide vs semaglutide for adults with type 2 diabetes: a systematic review and network meta-analysis of randomised controlled trials, Diabetologia, National Library of Medicine, 2024 [accessed 26 February 2025]

Efficacy and safety of semaglutide on weight loss in obese or overweight patients without diabetes: A systematic review and meta-analysis of randomised controlled trials, Frontiers, National Library of Medicine, 2022 [accessed 26 February 2025]

Semaglutide vs Tirzepatide for Weight Loss in Adults with Overweight or Obesity, JAMA Internal Medicine, National Library of Medicine, 2024 [accessed 26 February 2025]

Tirzepatide 10 and 15 mg compared with semaglutide 2.4 mg for the treatment of obesity: An indirect treatment comparison, Diabetes, Obesity and Metabolism, National Library of Medicine, 2023 [accessed 26 February 2025]

Mounjaro, EMC [accessed 15 June 2025]

Ozempic, EMC [accessed 15 June 2025]

Four-dose Mounjaro “KwikPen” approved by MHRA for diabetes and weight management, GOV.UK, [accessed 26 February 2025]