Liraglutide and semaglutide are both GLP-1 receptor agonists developed by Novo Nordisk, and both have FDA approvals covering type 2 diabetes and, at different doses, chronic weight management. But they're far from interchangeable, and a head-to-head trial has directly compared them.

Two Generations of the Same Drug Class

Liraglutide came first. It was FDA-approved for type 2 diabetes in 2010 under the brand name Victoza and for chronic weight management in 2014 at a higher dose under the brand name Saxenda. It requires a once-daily injection because of its relatively short half-life. Semaglutide followed: approved for type 2 diabetes in 2017 as Ozempic, as a once-daily oral tablet for diabetes in 2019 as Rybelsus, and for chronic weight management in 2021 as Wegovy (a higher-dose oral tablet for weight management arrived more recently, discussed elsewhere on this site). Structural modifications to semaglutide give it a much longer half-life, around a week, allowing once-weekly injectable dosing instead of daily.

What the Head-to-Head Trial Found

The STEP 8 trial directly compared semaglutide 2.4 mg against liraglutide 3.0 mg, both at their respective weight-management doses, in adults with overweight or obesity who did not have diabetes, over 68 weeks. Semaglutide produced a mean body weight reduction of 15.8%, more than double liraglutide's 6.4%. Notably, fewer people stopped semaglutide because of side effects, 3.2%, compared with 12.6% who discontinued liraglutide for that reason, even though a similar share of each group reported some gastrointestinal side effect (84.1% for semaglutide versus 82.7% for liraglutide). That combination, more weight loss with a lower discontinuation rate, is part of why semaglutide and the newer drugs built on similar chemistry have displaced liraglutide as the default choice for new prescriptions in this class.

Why the Difference

Both drugs activate the same GLP-1 receptor, but semaglutide's structural modifications, including changes that increase its binding to albumin in the blood, extend how long it circulates and appear to produce a stronger, more sustained appetite-suppressing effect at the doses used in these trials. The daily-versus-weekly dosing difference likely also affects real-world adherence outside of a trial setting, though STEP 8 was a supervised trial where both drugs were taken as directed, so the efficacy gap mostly reflects the drugs' direct effects rather than adherence differences alone.

Where Liraglutide Still Fits

Liraglutide hasn't been withdrawn from the market, and it remains an FDA-approved option for both diabetes and weight management. It can still be a reasonable choice for some patients, including those who've had side effects on semaglutide or whose insurance coverage differs between the two drugs. It has also been studied for longer, with a correspondingly longer real-world safety record.

The Bottom Line

Semaglutide's head-to-head data against liraglutide is about as clean a comparison as this drug class offers: a direct trial, similar dosing philosophy, and a clear result favoring semaglutide on both effectiveness and tolerability. That doesn't make liraglutide obsolete or unsafe, but it explains why it's no longer most clinicians' first choice when starting a new patient on a GLP-1 medication. Which drug is appropriate for a given person depends on individual medical history and prior response, which a prescribing physician is best positioned to weigh.