Going by the clinical trial results we have so far, retatrutide may be the most effective weight loss medicine yet. After 48 weeks on retatrutide, people lost up to 24.2% of their body weight. On Mounjaro, the estimated average weight loss at 48 weeks is around 20.5%, based on data from a 72-week trial (since the studies had different designs and sample sizes, it's not possible to compare them like-for-like.)
Unlike Mounjaro though, retatrutide is yet to be approved and is still undergoing clinical trials. We’re still learning about how it affects the body—and we don’t know what doses it will be available in.
This last point is important. Dosing schedules are carefully chosen to ensure that the medicine is effective without causing unmanageable side effects. Clinical research is ongoing, but here’s what we know so far about retatrutide dosing for weight loss.
What is retatrutide?
Retatrutide is a new weekly weight loss injection that’s in development. Like Saxenda, Wegovy and Mounjaro, it makes you feel full so you eat less.
Though it works in a unique way. Saxenda and Wegovy—which use the active ingredients liraglutide and semaglutide, respectively—act like the natural hunger hormone GLP-1, while Mounjaro (tirzepatide) mimics the behaviour of GLP-1 as well as another hormone, GIP.
But retatrutide brings on the effects of three hormones: GLP-1, GIP, and GCG (aka glucagon). This triple effect suggests that it’s the most potent medicine of the bunch. Though we’re yet to see any research comparing it to currently available medicines head-to-head.
Still, if you're curious how these medications differ, check out our guide to retatrutide, tirzepatide, and semaglutide.
FYI: retatrutide is also being studied as a type 2 diabetes treatment.
Retatrutide dosing schedule
There’s no official schedule just yet—which means that we can’t give you a retatrutide dosage chart (sorry). But per clinical research, it looks like you would start retatrutide on a lower dose and gradually be moved up, just like with other weight loss injections.
Retatrutide dosage facts (so far)
- Starting dose: 1mg or 2mg weekly (based on phase II trials)
- Dose escalation: Increased every 4 weeks
- Maximum dose: Up to 12mg weekly in trials
- Maintenance dose: Varies by individual (4mg to 12mg in studies)
In a phase II trial, people were put in groups and assigned to different doses. A total of five retatrutide weekly doses were used in the study: 1mg, 2mg, 4mg, 8mg and 12mg.
For those who were due to receive retatrutide doses of 4mg or higher, they started on a lower strength and were gradually dialled up every four weeks, for up to 12 weeks. Most people started on 1mg or 2mg.
Why do I need to follow a retatrutide dosing schedule?
If you were new to running, would you attempt to run a marathon right away? Of course not. You would need to train your body by gradually running longer distances, until you were ready to tackle 26.2 miles.
It’s the same principle with retatrutide. You start on a lower dose so your body can adjust to the medicine—and then handle higher strengths down the line. This helps to reduce your risk of side effects.
What is the retatrutide maintenance dose?
We can’t say just yet. Because clinical research is still going on, we don’t know which doses of retatrutide will be available—let alone which would be the typical weight loss maintenance dose.
But in the phase II trial we mentioned earlier, some people were on a 12mg as the maximum dose.
The maximum tolerated dose is the strength of a medicine where it’s working like it’s supposed to without causing troublesome side effects. And because people can respond differently to a medicine, that dose might vary from person to person. Your provider will confirm what your maintenance dose is.
Your weight loss journey
Retatrutide isn’t due to hit the UK market until at least mid-2026. Yet there’s a bunch of other weight loss medications available right now that could help you reach your goals.
You can get them posted to you each month when you sign up for our weight loss programme. Our dedicated team of clinicians and coaches will also work with you to transform your lifestyle—while cheering you on all the way.
Take our short quiz to find out if you’re eligible. We’ll review your results and come back to you within minutes.
¹
