How Much Weight Can You Lose in a Month With Mounjaro?

At a glance

• Clinical trials with Mounjaro (tirzepatide) showed patients’ weight loss percentages at 5mg, 10mg and 15mg doses were 15%, 19.5% and 20.9% respectively (at 72 weeks). 
• Theoretically, this would equate to just under or over 1% weight loss in a 4-week period depending on the dose. 
• Actual weight loss percentage between patients can be significantly different.

Before we dive deeper into this question, it is important to be aware that weight loss for each person can vary substantially. Each of us reacts to medicines such as Mounjaro differently, not to mention our unique body fat composition which is further influenced by diet and exercise.

Is Mounjaro effective?

The landmark trial for tirzepatide (Mounjaro) was known as the SURPASS-2 trial, which was a direct head-to-head trial with another drug in the glucagon-like peptide 1 (GLP-1) class: semaglutide (Wegovy).

One key research of this trial was to evaluate if Tirzepatide had a positive outcome on glycated haemoglobin in diabetic patients. The results were published in the New England Journal of Medicine. Tirzepatide was superior to semaglutide at all dose levels (5mg, 10mg and 15mg) for reducing glycated haemoglobin, a long-term measure for blood glucose control. Compared to semaglutide, patients on tirzepatide also lost more body weight.

Does Mounjaro help you lose weight?

After the positive results of the SURPASS-2 trial, another randomised control trial (SURMOUNT-1) was conducted a year later and published in the same journal. This time, the key research outcome was obesity.

The trial was double-blinded, phase 3 and had 2539 patients once weekly tirzepatide was compared to a placebo for 72 weeks, including the dose-escalation period lasting 20 weeks.

Key results from the SURMOUNT-1 trial:

Results clearly show that tirzepatide leads to more weight loss than placebo regardless of dose.

What does this mean for you?

The amount of weight you lose in a month depends on what stage and dose of treatment you are at.

Mounjaro is taken once weekly. To reduce side effects, the current dose should be taken for at least a month before increasing. The Summary of Product Characteristics for Mounjaro recommends 5mg, 10mg and 15mg as maintenance doses.

The SURMOUNT-1 trial lasted 72 weeks (roughly 18 months). From the results above, at 72 weeks:

From this data, the predicted average weight loss in 4 weeks is calculated by dividing 72 by 18 (every 4 weeks).

For example, if an obese male patient weighed 113kg, this patient could lose just under or over 1kg in a month depending on the dose taken. Note this is a theoretical assumption induced from the data. In practice, there are many reasons why this figure could vary.

Which factors could influence the percentage of weight loss with Mounjaro?

One factor is the dose escalation regime. Here is an example Mounjaro dosage regimen:

• Month 1: 2.5mg once weekly
• Month 2: 5mg once weekly
• Month 3: 7.5mg once weekly
• Month 4: 10mg once weekly

The doses are different despite the same treatment duration hence the weight loss percentage will inevitably change between the doses. You would expect a higher weight loss percentage with the higher maintenance doses e.g. 15mg once weekly. However, this can take a few months.

Another factor is the ‘optimal’ dose. The clinical data recommends a maximum of 15mg weekly which is only achievable after several months of treatment. Compared to someone taking Mounjaro initially for the first month, your percentage weight loss would likely be different if you were on month 6 of treatment for example.

Conclusion

Mounjaro has shown efficacy to help lose weight but it is important not to rush results. Increasing the doses too quickly can lead to common side effects such as nausea, constipation and diarrhoea.

Your weight loss journey should also incorporate lifestyle changes; a healthy diet and exercise plan should not be underestimated. Alongside continued Mounjaro use at the advised doses, you should see a gradual decline in weight with ongoing treatment duration.

Authored & Reviewed By

Mohamed Imran Lakhi

MPharm - Lead Pharmacist

Imran Lakhi is the superintendent pharmacist and founder at Prescription Doctor. He has been at the core of our team.

Published on: 21/06/2024 Reviewed on: 21/06/2024