Wegovy vs Mounjaro: Understanding the Differences

Both Wegovy and Mounjaro are licensed for weight loss and are prescription only medications. You should never get these medications without a prescription. Both medications mimic the GLP-1 hormone that makes people feel full and reduces cravings, and both are taken as a once weekly injection. So how are they different?

All drugs have a chemical name, the name of the actual drug, and a trade or 'brand' name, the name that the manufacturers have given it. Wegovy contains the medicine semaglutide, whilst Mounjaro contains the medicine tirzepatide. Whilst Wegovy works on one receptor, the GLP-1 receptor, tirzepatide works on two: the GLP-1 receptor and the GIP receptor. Both of these receptors are involved in stabilising blood sugar levels and helping patients feel fuller for longer.

One of the questions people most want answered is which medication leads to more weight loss. Based on the clinical trial data, Mounjaro appears to have a slight edge. In the SURMOUNT trials, people taking the highest dose of tirzepatide lost an average of around 20% of their body weight over roughly eighteen months. In the STEP trials with semaglutide, people lost an average of around 15% of their body weight over a similar timeframe.

However, it's crucial to understand what these averages mean in practice. These are averages, which means some people lost much more and some people lost less. There were people in the semaglutide trials who lost 25% or more of their body weight, and there were people in the tirzepatide trials who lost less than 10%. Individual responses vary enormously.

Both medications can cause similar side effects, with nausea being the most common complaint, particularly when starting treatment or increasing doses. Some people report that Mounjaro causes slightly less nausea than Wegovy, possibly because the addition of GIP receptor activation doesn't slow gastric emptying quite as much as GLP-1 activation alone. However, this isn't universal.

One consideration is that because Mounjaro is a newer medication, we have slightly less long term safety data compared to Wegovy. Semaglutide has been available for diabetes treatment since 2017, so we have several more years of experience with it. Additionally, semaglutide has been shown in the SELECT trial to reduce cardiovascular risk. Mounjaro hasn't yet been tested in a comparable cardiovascular outcomes trial, though one is ongoing.

The honest answer is that for many people, either medication could work well. The choice often comes down to a combination of factors including what your prescribing doctor recommends based on your individual circumstances, which medication is available and affordable to you, and sometimes simply which one you feel more comfortable with. The good news is that both medications represent a genuine breakthrough in weight management, offering real hope to people who have struggled for years.