If you’ve been looking into prescription weight loss treatments, you may have come across Wegovy, Mounjaro, and more recently, Orforglipron (brand name Foundayo). All three work with your body’s natural hunger signals to help reduce appetite and support weight loss.
Both Wegovy and Orforglipron do this by activating GLP-1 receptors, but they contain different medicines that are absorbed by the body differently. Mounjaro is slightly different yet again, targeting both GLP-1 and another hormone known as GIP.
These differences might sound technical, but they change how the treatments are taken, how effective they are, and which might suit you best.
Please be aware that Orforglipron (Foundayo) has not yet been approved for use in the UK and is awaiting approval by the MHRA. This article is for informational purposes only.
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In this article:
What do all three medicines have in common?
How do they work differently?
How are they taken?
How effective are they for weight loss?
How do side effects compare?
Which might be right for you?
What do all three medicines have in common?
Wegovy, Mounjaro, and Orforglipron all work by mimicking natural hormones that control appetite and fullness. In doing so, they help to:
Slow down how quickly food leaves the stomach
Reduce hunger signals in the brain
Increase feelings of fullness
Make it easier to eat smaller portions
For many people, this changes how they think about food. Cravings often feel less intense with less “food noise” and eating the right amount of balanced food can require less effort. Over time, this typically leads to a calorie deficit and gradual weight loss.
How do they work differently?
All three affect appetite in a similar way, but what’s happening inside the body isn’t identical.
Orforglipron vs Wegovy
Wegovy and Orforglipron both mimic the same appetite-regulating hormone, GLP-1. But they are built differently, which affects how they are absorbed and used by the body:
Orforglipron is a non-peptide, small-molecule medicine. Its structure allows it to pass through the digestive system easily, which is why it can be taken at any time of day as a once-daily tablet, without food and water restrictions.
Wegovy contains Semaglutide, which is a peptide-based medicine. Peptide medicines are easily broken down in the digestive system, making them harder for the body to absorb as tablets. This is why injectable semaglutide became available first, and why oral Semaglutide comes with strict timing instructions.
In simple terms, they work through the same GLP-1 pathway, but their different structures change how the body absorbs them and how they fit into day-to-day life.
Orforglipron vs Mounjaro
Mounjaro contains the medicine Tirzepatide, which is another peptide-based medicine with a structure more similar to Semaglutide than Orforglipron.
However, the bigger difference is its target in the body. Like the others, Mounjaro activates the GLP-1 pathway to support appetite control. But it also targets a second hormone called GIP. This “dual action” can have a stronger effect on appetite and metabolism for some people
Orforglipron only targets GLP-1, so while there is overlap in how the medicines work, Mounjaro acts on a broader hormone pathway.
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How are they taken?
One of the biggest practical differences between these treatments is how they fit into your routine.
Orforglipron is taken as a once-daily tablet and can be taken with or without food. It does not come with strict timing or water instructions.
Wegovy is most commonly used as a once-weekly injection for weight loss in the UK.
The Wegovy pill is a once-daily tablet for weight loss that has now been approved in the UK and is available for pre-order.
Mounjaro is taken as a once-weekly injection, with doses increased gradually over time.
For some people, weekly injections feel simpler and easier to remember. For others, taking a tablet for weight loss may feel more manageable day to day. These medicines should be taken indefinitely to maintain results, so it’s about finding a treatment that you can use consistently.
How effective are they for weight loss?
Clinical trials give us a helpful idea of what these treatments can achieve. On average:
Orforglipron — around 12% weight loss from starting body weight over 72 weeks based on higher doses tested before US approval (1)
Wegovy Injection — around 15% weight loss from starting body weight over 68 weeks at the standard 2.4mg injectable dose, around 19% weight loss at the higher 7.2mg dose (2-3).
Wegovy pill — around 16% weight loss from starting body weight over 64 weeks on the highest dose of 25mg (6).
Mounjaro — around 20% weight loss from starting body weight over 72 weeks at the highest 15mg Tirzepatide dose (4)
Real world glp-1 results can vary and some people lose less weight than the average, while others lose more. Progress is also gradual and tends to become more noticeable as you reach higher doses, so the “best” option for you isn’t always the one with the highest clinical trial average.
All three treatments lead to meaningful weight loss. What matters most is finding a treatment you can stay consistent with and feel comfortable using.
How do side effects compare?
Because Orforglipron, Wegovy, and Mounjaro all affect similar hormones, their side effects are broadly alike. The most common include digestive symptoms like:
Nausea
Diarrhoea
Vomiting
Constipation
GLP-1 side effects are usually most noticeable when starting treatment or increasing the dose, and often improve as your body adjusts.
The likelihood of experiencing these side effects is also similar. In studies, around 60–69% of people taking Orforglipron reported digestive symptoms, compared with around 70–75% using Wegovy (1,5). For Mounjaro, around 80% of people reported side effects overall, most of which were digestive (5).
However, this doesn’t mean your experience will be the same across each treatment. Most people find they tolerate one medicine better than another.
Which might be right for you?
Choosing between these treatments isn’t just about how they work.
If you want a weight loss treatment that’s already available in the UK, Wegovy and Mounjaro injections are current options.
If you prefer a tablet instead of injections, Orforglipron or the Wegovy Pill may be appealing. Wegovy tablets are now licensed and pre-orders are open. Orforglipron is not yet licensed in the UK and will likely be available towards the end of 2026.
The right choice also depends on your medical history, any other medicines you’re taking, your lifestyle, and how you feel about using injections. In a consultation, your clinician can help you weigh these factors up and recommend a treatment that’s safe and suitable for you.
If you’re unsure, you’re not expected to decide on your own. The expert team and Oxford Online Pharmacy are here to help.
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References
Wharton S, Aronne LJ, Stefanski A, Alfaris NF, Ciudin A, Yokote K, et al. Orforglipron, an Oral Small-Molecule GLP-1 Receptor Agonist for Obesity Treatment. New England Journal of Medicine. 2025 Sep 16;
Wilding JPH, Batterham RL, Calanna S. Once-Weekly Semaglutide in Adults with Overweight or Obesity. The New England Journal of Medicine [Internet]. 2021 Feb 10;384(11):989–1002.
Wharton S, Freitas P, Jøran Hjelmesæth, Kabisch M, Kandler K, Ildiko Lingvay, et al. Once-weekly semaglutide 7·2 mg in adults with obesity (STEP UP): a randomised, controlled, phase 3b trial. The Lancet Diabetes & Endocrinology [Internet]. 2025 Sep 1; Available from:
Jastreboff AM, Aronne LJ, Ahmad NN, Wharton S, Connery L, Alves B, et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine [Internet]. 2022 Jun 4;387(3):205–16.
Ghusn W, Hurtado MD. Glucagon-like Receptor-1 agonists for obesity: Weight loss outcomes, tolerability, side effects, and risks. Obesity Pillars. 2024 Dec;12:100127.
Wharton S, Ildiko Lingvay, Bogdanski P, Duque R, Jacob S, Karlsson T, et al. Oral Semaglutide at a Dose of 25 mg in Adults with Overweight or Obesity. New England Journal of Medicine. 2025 Sep 17;393(11):1077–87.