By Dr. Asnat Raziel, bariatric surgeon specializing in obesity treatment, metabolic health and healthy longevity; Director of the Multidisciplinary Center for Obesity Treatment, Assia Medical, Assuta Ramat HaChayal, Tel Aviv
Mounjaro vs. Wegovy: why the difference matters
Mounjaro vs. Wegovy is a question on the mind of almost everyone starting medication for obesity. Wegovy contains semaglutide, and Mounjaro contains tirzepatide. Both are given as a once-weekly injection, and both lead to significant weight loss. They are not, however, the same drug.
In my clinic, I see every day how an informed choice can change the course of a person’s life. It improves health and prevents complications in the long run. So I have gathered the latest data here, to help you come to the conversation with your doctor well prepared.
Two mechanisms, one goal
Both drugs mimic natural hormones that the gut releases after a meal. Wegovy activates the receptor for GLP-1, a hormone that regulates appetite, digestion and blood sugar. In this way it reduces hunger, helps you feel full sooner and lowers calorie intake. It may also weaken cravings for sweet, salty or fatty foods.
Mounjaro, by contrast, acts on two receptors: GLP-1 and also GIP, another hormone that influences appetite and metabolism. This dual action slows stomach emptying, increases satiety and improves insulin release after meals. Wegovy was approved for obesity in the United States in 2021. Tirzepatide was approved for diabetes in 2022 and for obesity at the end of 2023.
Mounjaro vs. Wegovy for weight loss
In the STEP 1 trial, patients on Wegovy 2.4 mg lost an average of 14.9% of their body weight after 68 weeks. In the SURMOUNT-1 trial, Mounjaro at 15 mg led to a 20.9% loss after 72 weeks. These were separate trials, though, so comparing them is only indirect.
The head-to-head comparison came in 2025. The SURMOUNT-5 trial enrolled 751 adults with obesity who did not have diabetes. After 72 weeks, body weight fell by 20.2% with Mounjaro, compared with 13.7% with Wegovy. Waist circumference also shrank far more with Mounjaro: 18.4 cm versus 13.0 cm. In other words, at the standard doses, Mounjaro led to considerably greater weight loss.
What’s new with Wegovy: a higher dose and a pill
Since then, Wegovy has gained two new options. First, the US Food and Drug Administration (FDA) approved a weekly dose of 7.2 mg in March 2026. In the European Union and the UK, this dose had already been approved earlier. In the STEP UP trial, average weight loss reached 20.7% after 72 weeks among those who stayed on treatment. You’ll find more details in my article on high-dose Wegovy.
Second, in December 2025 a daily 25 mg Wegovy pill was approved. In the OASIS 4 trial, participants lost 13.6% of their body weight after 64 weeks, compared with 2.2% on placebo. So for those who prefer not to inject, the Wegovy pill is an option worth reading about.
Approvals and health benefits
The two drugs have different approvals. According to the Wegovy prescribing information, the injection is approved for adults and for adolescents aged 12 and older with obesity. It is also approved to reduce cardiovascular risk in adults with heart disease and to treat inflammatory fatty liver disease (MASH) with liver scarring. The Zepbound prescribing information (Zepbound is the US brand name of tirzepatide for obesity), on the other hand, covers adults only. It also includes treatment of moderate to severe obstructive sleep apnea.
On the heart front, Wegovy reduced major cardiovascular events by 20% in patients with heart disease who did not have diabetes. In 2026, Mounjaro was approved to reduce cardiovascular risk in people with type 2 diabetes. Beyond that, both drugs improve blood pressure, blood lipids, joint pain and everyday functioning. I go into more detail in my article on weight-loss drugs and the heart.
Dosing and gradual titration
With both drugs, treatment starts at a low dose that is increased gradually. Wegovy starts at 0.25 mg a week and steps up every four weeks: 0.5, 1, 1.7 and 2.4 mg. If needed, the doctor can go up to 7.2 mg. Mounjaro starts at 2.5 mg for four weeks. After that, the dose rises by 2.5 mg each time, up to a maximum of 15 mg. This slow increase makes the drugs much easier to tolerate.
Side effects: Mounjaro vs. Wegovy
The side effects are similar and mainly involve the digestive system. According to the Wegovy prescribing information, nausea occurred in 44% of patients, diarrhea in 30%, and vomiting and constipation in 24%. In the Zepbound prescribing information, by comparison, nausea occurred in 25%-29% and diarrhea in 19%-23%, depending on the dose. These figures come from different trials, however, so no clear advantage should be inferred from them.
In most cases the side effects ease over time. Small meals, avoiding fatty foods and drinking enough fluids help a great deal. Sometimes slowing down the dose increase solves the problem. There are also rare risks: pancreatitis, gallbladder problems and kidney injury due to dehydration.
Both drugs are contraindicated in people with a personal or family history of medullary thyroid cancer or MEN2 syndrome. They are also contraindicated during pregnancy and in anyone allergic to their ingredients. In people with diabetes, Wegovy may, in rare cases, worsen retinopathy, diabetic damage to the retina. And what about mood? In 2026, the FDA requested removal of the warning about suicidal thoughts. The reason: an analysis of 91 trials with 107,910 participants showed no increase in risk.
Cost and coverage in Israel
In Israel, the price varies by dose, health fund (HMO) and supplementary insurance plan. Most health funds offer a discount through their supplementary insurance, but it usually requires prior approval. Prices are also updated from time to time, so it is worth checking with your health fund before starting treatment. I have gathered the details in my article on the price of Wegovy and Mounjaro.
A multidisciplinary approach: beyond the injection
The medication is only one part of the plan. First, you need a prescription from a doctor after an assessment of your BMI and related conditions. These drugs also work best alongside a balanced diet, at least 150 minutes of physical activity a week, stress management and good sleep. Close follow-up with a doctor and a dietitian makes it possible to adjust the dose, monitor side effects and make sure you get enough protein. Finally, emotional and behavioral support helps you cope with emotional eating and prevent weight regain.
How to choose: Mounjaro vs. Wegovy in practice
The choice begins with your goals. When the aim is substantial weight loss, Mounjaro has the edge in the trials. On the other hand, for people with heart disease who do not have diabetes, Wegovy has direct evidence from SELECT. Sleep apnea may tip the balance toward Mounjaro. Adolescents, meanwhile, would receive Wegovy, and those who prefer a pill would choose the Wegovy pill. Ultimately, personal tolerance, cost and coverage also shape the decision.
The bottom line on Mounjaro vs. Wegovy
Wegovy and Mounjaro are a breakthrough in obesity treatment. Mounjaro leads to greater weight loss, while Wegovy now offers a wide range of doses and forms. Both have evidence of heart protection, each in a different population. So the choice between Mounjaro and Wegovy is not a question of “good” or “bad” but of personal fit. Before you start, learn what you need to know ahead of treatment and have an open conversation with a doctor who specializes in obesity.
The information in this article is general and does not replace personal medical advice.
References
Once-Weekly Semaglutide in Adults with Overweight or Obesity
Tirzepatide Once Weekly for the Treatment of Obesity
Tirzepatide as Compared with Semaglutide for the Treatment of Obesity
Wegovy HD (semaglutide 7.2 mg) approved in the US, providing 20.7% mean weight loss
Oral Semaglutide at a Dose of 25 mg in Adults with Overweight or Obesity
WEGOVY (semaglutide) – Prescribing Information
ZEPBOUND (tirzepatide) – Prescribing Information
The STEP and OASIS trials were funded by Novo Nordisk. The SURMOUNT trials were funded by Eli Lilly.
