Mounjaro, Wegovy, and Retatrutide are three of the most talked-about prescription weight-loss injections right now. All three require a clinical assessment before they can be prescribed, but they work differently and aren’t approved for the same uses. Here’s how they compare.
How they work
| Medication | Active ingredient | Mechanism |
|---|---|---|
| Mounjaro | Tirzepatide | Dual GIP/GLP-1 receptor agonist |
| Wegovy | Semaglutide | GLP-1 receptor agonist |
| Retatrutide | Retatrutide | Triple GLP-1/GIP/glucagon receptor agonist |
Adding a third active pathway is what sets Retatrutide apart: the glucagon-receptor component contributes an energy-expenditure effect on top of the appetite suppression that all three medications share. See our full Mounjaro vs Wegovy breakdown for more detail on how those two compare specifically.
Weight loss in trial data
Trial results aren’t directly comparable across separate studies, but general trends show Wegovy (semaglutide) produces meaningful weight loss on its own, Mounjaro’s dual mechanism has shown somewhat greater average weight loss in head-to-head data against semaglutide, and Retatrutide’s triple mechanism reported the largest reductions of the three in its own Phase 2 trial — though it’s the newest of the three and has less long-term real-world data behind it.
Eligibility
All three follow the same basic eligibility criteria: a BMI of 30 or above, or 27 or above with a weight-related condition such as high blood pressure or type 2 diabetes. Eligibility for any of them is confirmed through an online medical questionnaire, reviewed by a licensed physician, before a prescription is issued — see our full eligibility guide.
Dosing
Each is a self-administered injection, started at a low dose and increased gradually to reduce side effects like nausea. See the Mounjaro dosing schedule for a worked example of how titration typically progresses. Never start, stop, or change your dose without direction from your prescriber.
Side effects
All three share a similar side-effect profile — nausea, diarrhoea, and constipation are the most commonly reported, usually easing as your body adjusts. See our Mounjaro and Wegovy side-effect guides for details on what to expect and when to contact your prescriber.
Which one is right for you?
The right choice depends on your medical history, prior response to GLP-1 medications, and what your prescriber recommends after reviewing your questionnaire — this isn’t something to decide on trial data alone. Start with a free online consultation and your prescriber will help you weigh the options.