How does Wegovy compare to Saxenda in terms of effectiveness?

In a head-to-head trial published in The New England Journal of Medicine, people taking Wegovy lost on average about 15.8% of their body weight over 68 weeks compared with 6.4% for those on Saxenda (liraglutide). This makes Wegovy the more effective of the two for weight loss in most cases.

Two GLP-1 medicines, one key difference

Both Wegovy and Saxenda belong to the same class of medicines, known as GLP-1 receptor agonists. They work by mimicking a natural hormone that reduces appetite, slows digestion, and helps regulate blood sugar. The main difference is that Wegovy contains semaglutide, while Saxenda contains liraglutide. This difference in molecule and dosing explains the gap in results seen in trials.

What the trials revealed

A large head-to-head study directly compared the two drugs. Participants taking semaglutide 2.4 mg (Wegovy) lost nearly 16% of their body weight on average over 68 weeks. Those taking liraglutide 3 mg (Saxenda) lost just over 6%. These results, published in The New England Journal of Medicine, confirmed what earlier studies had suggested: semaglutide is more powerful for weight reduction at the doses used in weight-management programmes.

Why semaglutide works differently

Semaglutide has a longer half-life in the body, meaning it lasts longer and can be given once a week. Liraglutide, by contrast, is taken as a daily injection. This not only affects convenience, but also the overall effect. The steadier weekly dosing of semaglutide seems to provide a stronger and more consistent appetite-suppressing signal, which helps explain the greater average weight loss.

What NICE and the NHS say

NICE guidance reflects these differences. Saxenda was the first GLP-1 medicine to be approved for weight management in the UK, but its use is more limited and often requires private funding. Wegovy is now recommended on the NHS for people with a BMI above 35 and related health conditions, or in some cases above 30 if certain criteria are met. The stronger evidence base from the STEP trials underpins this decision, making semaglutide the preferred GLP-1 option for weight management services.

Considering side effects and tolerability

Both medicines have similar side-effect profiles, since they act on the same hormonal pathway. Nausea, diarrhoea, and constipation are common, especially when first starting. Some people tolerate one better than the other, though in practice most find that side effects ease with time. The difference in frequency — daily for Saxenda, weekly for Wegovy — also matters for day-to-day convenience and adherence.

Real-world experience

People who have tried both often describe Wegovy as more manageable because of the once-weekly pen and the stronger effect on appetite. For others, Saxenda has been a useful stepping stone, especially when Wegovy was not yet available. Clinicians often highlight that what matters is not just trial averages, but whether the medicine works for the individual and can be continued safely.

Key takeaways

While both Wegovy and Saxenda belong to the same class of treatments, semaglutide consistently produces greater average weight loss than liraglutide in clinical trials. Wegovy also offers the convenience of weekly dosing, while Saxenda requires daily injections. Both have a role, but NHS guidance now prioritises Wegovy because of its stronger evidence base and effectiveness. For people considering these medicines, the main difference comes down to outcomes and accessibility.