Two answers to the same problem
Natural GLP-1 is broken down within minutes. The Saxenda® label puts its half-life at 1.5 to 2 minutes, because the enzymes DPP-4 and neutral endopeptidase degrade it [1]. Both liraglutide and semaglutide are changed versions of GLP-1 designed to survive much longer while still activating the same receptor.
The labels describe liraglutide as 97% similar in amino acid sequence to human GLP-1, and semaglutide as 94% similar [1][2]. The differences lie in how each one was modified to last.
How the molecules differ
According to the Saxenda® label, liraglutide has arginine in place of lysine at position 34, and a 16-carbon fatty acid (palmitic acid) attached through a glutamic acid spacer at position 26. Its precursor is made using yeast [1].
Semaglutide, as described in the Ozempic® and Wegovy® labels, is modified at position 8 to resist DPP-4 and carries an 18-carbon fatty di-acid at position 26 through a spacer. More than 99% is bound to albumin, which slows its removal and protects it from degradation [2][3].
Side by side, from the labels
| Feature | Liraglutide (Saxenda®) | Semaglutide (Wegovy®) |
|---|---|---|
| Similarity to human GLP-1 | 97% [1] | 94% [2] |
| Elimination half-life (section 12.3) | About 13 hours [1] | About 1 week [2] |
| How often taken | Once daily injection [1] | Once weekly injection (tablets taken daily) [2] |
| Share of a dose reaching the blood | About 55% [1] | 89% [2] |
| Peak after a dose | About 11 hours [1] | 1 to 3 days [2] |
| Protein binding | More than 98% [1] | More than 99% (albumin) [2] |
| How it leaves the body | Broken down like large proteins; no intact liraglutide found in urine or faeces [1] | Broken down; about 3% leaves unchanged in urine [2] |
| Still in the circulation after the last dose | Not stated in the label [1] | About 5 to 7 weeks after 2.4 mg or 7.2 mg [2] |
| Pregnancy (section 8) | Stop when pregnancy is recognised [1] | Stop at least 2 months before a planned pregnancy [2] |
| Label-described escalation | Weekly steps, reaching 3 mg in week 5 [1] | 4-week steps, maintenance from week 17 [2] |
Daily or weekly in practice
The half-life explains the schedule. With a 13-hour half-life, liraglutide is suited to once-daily dosing; the Saxenda® label says it can be injected at any time of day, regardless of meals [1]. With a half-life of about a week, semaglutide is injected once weekly, and the Wegovy® label estimates that it is still circulating 5 to 7 weeks after the final dose [2].
Missed doses are handled differently too. The Saxenda® label says to simply continue with the next daily dose, but to restart at the lowest dose if more than 3 days have passed. The Wegovy® label uses a 2-day window before the next weekly dose, and restarts the steps lower after two or more missed weeks [1][2].
Both labels ask you to rotate injection sites. The Saxenda® label adds a reason not found in the Wegovy® label: rotating within the same region lowers the risk of cutaneous amyloidosis, a protein deposit under the skin reported after marketing [1][2].
Two brand families
- Liraglutide: Saxenda® for weight management; Victoza®, at doses up to 1.8 mg a day, for type 2 diabetes in adults and children aged 10 and older and for lowering cardiovascular risk in adults with type 2 diabetes and heart disease [1][4]. MedlinePlus also lists Xultophy®, a combination with insulin degludec [12].
- Generic liraglutide: the FDA approved the first generic referencing Victoza® on 23 December 2024, and one referencing Saxenda® on 27 August 2025 [10][11].
- Semaglutide: Wegovy® injection and tablets for weight, heart risk and, as an injection, MASH; Ozempic® injection for type 2 diabetes; Rybelsus® and Ozempic® tablets for type 2 diabetes [2][3][5].
- NIDDK describes both pairs the same way: one weight-management brand and, under another name and dose, a diabetes brand [13].
Trials that compared them directly
Most of each label rests on placebo-controlled trials. Three randomised trials put the two molecules head to head, each with its own doses, people and length. They are summarised below from the published abstracts and, for PIONEER 4, from the tablet label.
- STEP 8 used the doses of the two weight-management products on this page, semaglutide 2.4 mg weekly (the Wegovy® maintenance dose) and liraglutide 3 mg daily (the Saxenda® dose) [1][2][6].
- SUSTAIN 10 and PIONEER 4 did not: they tested diabetes doses, a weekly semaglutide 1.0 mg injection (an Ozempic® dose) or semaglutide tablets 14 mg (a Rybelsus® strength) against liraglutide 1.2 mg or 1.8 mg daily (Victoza® doses), in adults with type 2 diabetes [3][4][5][7].
- Each result in the table below applies only to the doses tested. SUSTAIN 10 used 1.2 mg of liraglutide, below the 1.8 mg maximum in the Victoza® label [4][7].
- STEP 8 was open-label for the semaglutide-versus-liraglutide comparison, and Novo Nordisk, which makes both medicines, employed several of its authors [6].
- In SUSTAIN 10, side effects led to stopping more often on semaglutide (11.4% vs 6.6%) [7].
- Group averages do not show which medicine will suit a particular person; that is a decision for a prescriber.
| Trial and design | People | Compared | Length | Main result |
|---|---|---|---|---|
| STEP 8, open-label, phase 3b [6] | 338 adults with obesity or overweight, without diabetes | Semaglutide 2.4 mg weekly vs liraglutide 3 mg daily, each with diet and activity | 68 weeks | Weight −15.8% vs −6.4%; stopped treatment for any reason 13.5% vs 27.6%; gut side effects 84.1% vs 82.7% [6] |
| SUSTAIN 10, open-label, phase 3b [7] | 577 adults with type 2 diabetes on 1 to 3 oral medicines | Semaglutide 1.0 mg weekly vs liraglutide 1.2 mg daily | 30 weeks | HbA1c −1.7 vs −1.0 points; weight −5.8 vs −1.9 kg; gut side effects 43.9% vs 38.3% [7] |
| PIONEER 4, double-blind, double-dummy [5] | 711 adults with type 2 diabetes on metformin, some with an SGLT-2 inhibitor | Semaglutide tablets 14 mg daily vs liraglutide 1.8 mg daily (and placebo) | 26 weeks | HbA1c −1.2 vs −1.1 points (non-inferior); weight −4.4 vs −3.1 kg [5] |
Side-effect tables in the two weight labels
The Saxenda® table comes from 5 placebo-controlled trials in 3,384 adults treated for up to 56 weeks; the Wegovy® table from 3 trials in 2,116 adults treated for up to 68 weeks [1][2]. These are separate trial programmes, so the columns are context, not a comparison; both labels say rates from different drugs’ trials cannot be compared directly [1][2].
| Reaction | Saxenda® programme: placebo / 3 mg | Wegovy® programme: placebo / 2.4 mg |
|---|---|---|
| Nausea | 13.8 / 39.3 [1] | 16 / 44 [2] |
| Diarrhoea | 9.9 / 20.9 [1] | 16 / 30 [2] |
| Constipation | 8.5 / 19.4 [1] | 11 / 24 [2] |
| Vomiting | 3.9 / 15.7 [1] | 6 / 24 [2] |
| Abdominal pain | 3.1 / 5.4 [1] | 10 / 20 [2] |
| Stopped because of an adverse reaction | 4.3 / 9.8 [1] | 3.2 / 6.8 [2] |
Checkpoints written into the labels
The Saxenda® label asks prescribers to check weight 16 weeks after starting in adults and to stop if at least 4% of baseline weight has not been lost. For children, it asks for a check after 12 weeks on the maintenance dose and a stop if BMI has not fallen by at least 1%. Adults who cannot tolerate 3 mg daily are taken off the medicine, because the lower doses are for titration only [1].
The Wegovy® label instead offers two maintenance doses for weight reduction, 1.7 mg or 2.4 mg, chosen by treatment response and tolerability, with a higher dose possible for some adults [2].
The European product information sets its own checkpoints. For Saxenda®, adults stop after 12 weeks on 3 mg if they have not lost at least 5% of their starting weight, and adolescents are re-evaluated if BMI has not fallen by at least 4%; for Wegovy®, adolescents are re-evaluated if BMI has not fallen by at least 5% after 12 weeks [8][9].
What the two labels share
Both carry a boxed warning about thyroid C-cell tumors seen in rodents, and both rule out people who have had MTC (a thyroid cancer) or whose relatives have, people with MEN 2, and people with a serious allergy to the medicine [1][2]. Both list pancreatitis, gallbladder disease, low blood sugar with insulin or sulfonylureas, kidney injury from dehydration, severe stomach side effects and aspiration during anaesthesia among their warnings [1][2].
Both also warn about a faster resting heart rate. In the weight trials, the Saxenda® label reports mean rises of 2 to 3 beats per minute and the Wegovy® label 1 to 4, measured in different ways [1][2]. Each label says it should not be combined with other GLP-1 receptor agonists [1][2].
No winner in the labels
Neither label compares the two medicines; each reports its own placebo-controlled trials, which differed in design and length. The head-to-head trials above answer narrower questions at fixed doses. A daily injection suits some routines and a weekly one suits others, and a prescriber weighs that with medical history, other medicines and response.
Saxenda®, Wegovy®, Victoza®, Ozempic®, Rybelsus® and Xultophy® are registered trademarks of Novo Nordisk A/S. PepLabo is not affiliated with or endorsed by Novo Nordisk.
When to get help
| Sign | Who to contact | How fast | Source |
|---|---|---|---|
| Ongoing, severe pain in the abdomen, which may spread to the back, with or without vomiting | Stop the injection and contact your prescriber straight away | Emergency | Saxenda® and Wegovy® labels, section 5.2 [1][2] |
| Your heart races or pounds at rest for several minutes | Your prescriber | Today | Saxenda® Medication Guide [1]; Wegovy® section 5.9 [2] |
| Pain in the upper abdomen with yellow skin or eyes, fever or pale, clay-coloured stools | Your prescriber | Today | Saxenda® Medication Guide [1] |
| You find out you are pregnant, or you are planning a pregnancy | Your prescriber | Today | Saxenda® section 8.1 [1]; Wegovy® section 8.3 [2] |
