In short
Overview
Mounjaro is generally the more effective of the two for weight loss. Whether it is the right one for you depends on three things that have nothing to do with the headline number.
Direct Answer
Mounjaro is tirzepatide, which acts on two receptors. Ozempic is semaglutide, which acts on one. Tirzepatide is more effective for weight loss and beat semaglutide 2.4 mg in a head to head trial.
But semaglutide is preferred if you have established cardiovascular disease without diabetes, because it is the only agent in the class with proven cardiovascular benefit in that group.
And tirzepatide is preferred if you have obstructive sleep apnoea, where it has shown improvement in sleep apnoea outcomes.
Who This Applies To
Which one is likely to be right
| Maximum weight loss the priority | Tirzepatide |
| Established cardiovascular disease, no diabetes | Semaglutide |
| Obstructive sleep apnoea | Tirzepatide |
| Type 2 diabetes | Either. Both have proven cardiovascular benefit in diabetes with established disease |
| Cost or availability is the constraint | Whichever you can sustain, which may be neither |
Option Comparison / Decision Criteria
What the trials show
Tirzepatide. In SURMOUNT-1, over 2500 adults with obesity and no diabetes, at 72 weeks: mean weight change of minus 15 per cent at 5 mg, minus 19.5 per cent at 10 mg and minus 20.9 per cent at 15 mg, against minus 3.1 per cent on placebo. 91 per cent of the 15 mg group lost at least 5 per cent, and 57 per cent lost 20 per cent or more. Results were sustained at three years.
Semaglutide. At 68 weeks, mean change of minus 15.8 per cent for 2.4 mg against minus 6.4 per cent for liraglutide 3 mg. In a network meta analysis it had the greatest odds of at least 5 per cent loss, odds ratio 9.82.
Head to head. Tirzepatide was more effective than semaglutide 2.4 mg. The higher semaglutide 7.2 mg dose was not included in that comparison.
Dosing
| Tirzepatide | 2.5 mg weekly for four weeks, then increases of 2.5 mg at minimum four week intervals, to a maximum of 15 mg |
| Semaglutide | 0.25 mg weekly for four weeks, then 0.5, 1, 1.7 and 2.4 mg at four week intervals |
Both use the minimum dose that achieves the weight loss you need, rather than automatically going to the maximum.
The cardiovascular difference, stated carefully
Semaglutide has shown improved cardiovascular outcomes in people without diabetes who have established cardiovascular disease. Tirzepatide reduces cardiovascular events in adults with type 2 diabetes and pre existing cardiovascular disease, but this has not been confirmed in people with obesity who do not have diabetes.
The absolute cardiovascular risk reduction is described as modest, so tirzepatide remains a reasonable alternative for someone in that group who prioritises weight loss.
Why an In-Person Physician Review Matters
The side effects are shared Both are monitored for nausea, vomiting, diarrhoea, constipation, reflux, pancreatitis and gallbladder disease.
Neither is gentler than the other in a way that decides the choice. Both need slower dose increases and monitoring for anyone with diabetic retinopathy. Why the choice is often made on access Cost and coverage are frequently the primary consideration in choosing an agent, and that is a recognised clinical factor rather than a compromise. Most of these drugs have no generic version. A drug you can continue for years beats a marginally better drug you have to stop, because stopping leads to regain of about 0.4 kg a month and a projected return to baseline within two years. What your goal implies Target of 15 per cent or more: you need one of these two Target under 15 per cent: liraglutide or orforglipron can often get you there, and may be more affordable What happens if the first choice does not work At 12 weeks on the maximum tolerated dose, if less than 4 to 5 per cent of body weight has gone, the medication is normally stopped and a different agent tried. Switching is a normal part of the process rather than a setback.
Frequently Asked Questions
Tirzepatide, generally. It beat semaglutide 2.4 mg head to head, and in SURMOUNT-1 the 15 mg dose gave 20.9 per cent mean loss at 72 weeks with 57 per cent of that group losing 20 per cent or more.
If you have established cardiovascular disease without diabetes, it is the only agent in the class with proven cardiovascular benefit in that group. Tirzepatide has not shown this in people with obesity who do not have diabetes.
Yes, toward tirzepatide. It has demonstrated improvement in sleep apnoea outcomes and holds regulatory approval in the United States for moderate to severe sleep apnoea in adults with obesity.
Broadly the same. Both are monitored for nausea, vomiting, diarrhoea, constipation, reflux, pancreatitis and gallbladder disease, and both need a gradual dose build up to keep the nausea manageable.
Evidence
Where this information comes from
Every figure on this page is taken from the sources below. All of them are free to read, so you can check them yourself.
- Ozempic: European public assessment report
- Semaglutide for managing overweight and obesity
- Obesity and overweight
This page is general medical information and does not replace a personal consultation. Trial results are averages across large groups, not a prediction for any one person.