Liraglutide: what it is, Saxenda and Victoza trial results, dosage and side effects

Liraglutide is a modified version of the human gut hormone glucagon-like peptide-1 (GLP-1). Native GLP-1 is broken down within minutes, which makes it useless as a drug. In 2000, Novo Nordisk chemists described a series of GLP-1 derivatives carrying a fatty acid chain that binds to albumin in the blood, protecting the peptide from degradation and slowing its clearance enough for once-daily injection ^[1]. The compound taken forward was coded NN2211. A 2002 study in healthy men measured its half-life at 12.6 hours after subcutaneous injection ^[2], and the current US label gives about 13 hours ^[13].

It was the first of the long-acting GLP-1 drugs to reach wide use, and it is the direct ancestor of semaglutide, which uses the same albumin-binding strategy with a longer fatty acid to reach once-weekly dosing. Newer drugs such as tirzepatide, retatrutide and the amylin analogue cagrilintide are often compared against liraglutide in trials, because it is the established benchmark. Our guide to GLP-1 brand names lists the products in this family.

Because liraglutide is a licensed medicine, the liraglutide peptide sold by research suppliers occupies a different position from investigational compounds like retatrutide: the real product exists, on prescription, and is now available as a generic in the US ^[15]. A research vial is not that product. See what research peptides are.

Liraglutide binds the GLP-1 receptor with potency similar to native GLP-1 ^[1]. Through that receptor it increases insulin release when glucose is high, suppresses glucagon, slows stomach emptying and reduces appetite. The albumin binding conferred by its fatty acid chain means that after injection it is absorbed slowly and cleared slowly, so a single daily dose gives steady blood levels; the 2002 phase 1 study found an accumulation index of 1.4 to 1.5 after seven daily doses, meaning steady-state levels are about 40% to 50% higher than after a first dose ^[2].

The weight effect comes mainly from reduced food intake. In the 2009 phase 2 obesity trial, liraglutide reduced weight at every dose from 1.2 mg to 3.0 mg in people without diabetes, and also lowered blood pressure and cut the prevalence of prediabetes by 84% to 96% at the higher doses over 20 weeks ^[3]. The doses used for weight management (3.0 mg) are higher than those used for diabetes (up to 1.8 mg), reflecting the dose-response for appetite rather than for glucose.

The first obesity trial, published in The Lancet in 2009, randomised 564 adults with a BMI of 30 to 40 and no diabetes to liraglutide 1.2, 1.8, 2.4 or 3.0 mg daily, placebo or orlistat for 20 weeks, all on a 500 kcal per day deficit diet. Mean weight loss was 4.8, 5.5, 6.3 and 7.2 kg on the four liraglutide doses, against 2.8 kg on placebo and 4.1 kg on orlistat, and 76% of those on 3.0 mg lost more than 5% of their weight against 30% on placebo ^[3].

The SCALE programme followed. SCALE Obesity and Prediabetes, in the New England Journal of Medicine in 2015, randomised 3,731 adults without diabetes, with a mean weight of 106.2 kg and BMI of 38.3, to liraglutide 3.0 mg or placebo for 56 weeks. Weight fell by 8.4 kg on liraglutide against 2.8 kg on placebo, a difference of 5.6 kg. In total 63.2% of the liraglutide group lost at least 5% of their weight against 27.1% on placebo, and 33.1% against 10.6% lost more than 10% ^[5]. The three-year extension of the same trial in 2,254 people with prediabetes found that liraglutide made time to a diabetes diagnosis 2.7 times longer, with 2% diagnosed on liraglutide against 6% on placebo by week 160, and weight loss of 6.1% against 1.9% at that point; about half of participants had withdrawn by then ^[8].

SCALE Maintenance asked a different question: 422 people who had already lost at least 5% on a low-calorie diet were randomised to liraglutide 3.0 mg or placebo for 56 weeks. Liraglutide produced a further 6.2% loss against 0.2% on placebo, and 81.4% kept off the initial loss against 48.9% on placebo ^[4]. SCALE Diabetes, in JAMA in 2015, randomised 846 adults with type 2 diabetes: weight fell by 6.0% on 3.0 mg, 4.7% on 1.8 mg and 2.0% on placebo over 56 weeks ^[6]. Weight loss with liraglutide in diabetes is consistently smaller than in people without diabetes.

Liraglutide results in children are more recent. In adolescents aged 12 to under 18 with obesity, 56 weeks of liraglutide 3.0 mg reduced the BMI standard-deviation score by 0.22 more than placebo, and 43.3% against 18.7% achieved at least a 5% BMI reduction; weight regain after stopping was greater on liraglutide ^[9]. In children aged 6 to under 12, a 2025 trial of 82 participants found BMI changed by −5.8% on liraglutide against +1.6% on placebo over 56 weeks ^[10].

LEADER is the trial that established liraglutide’s cardiovascular record. Published in the New England Journal of Medicine in 2016, it randomised 9,340 people with type 2 diabetes at high cardiovascular risk to liraglutide or placebo on top of standard care and followed them for a median of 3.8 years. The primary outcome, a composite of cardiovascular death, non-fatal heart attack and non-fatal stroke, occurred in 13.0% on liraglutide against 14.9% on placebo, a hazard ratio of 0.87. Cardiovascular death was lower (4.7% against 6.0%), as was death from any cause (8.2% against 9.6%) ^[7].

A prespecified secondary analysis of LEADER found fewer kidney outcomes on liraglutide, 268 against 337 events, driven mainly by fewer people developing persistent macroalbuminuria; rates of acute kidney injury were similar ^[12]. These outcome data are what distinguish liraglutide from the investigational peptides sold alongside it: they come from a trial designed to detect harm as well as benefit over years, and no research-grade product has anything comparable.

Blood levels reach steady state within about a week of daily dosing, given the liraglutide half-life of about 13 hours ^{[2] [13]}. Weight effects were measurable within the 20-week phase 2 trial ^[3], and most of the 56-week loss in SCALE Obesity had accrued well before the end, although the published abstract reports only the week 56 figure ^[5]. The licensed dose is reached by a five-week escalation, so the first month is spent at lower doses ^[13].

The label sets a stopping rule rather than an onset time: the EMA summary says treatment should be discontinued if adults have not lost at least 5% of their starting weight after 12 weeks on the full 3.0 mg dose ^[14].

For weight management, the Saxenda label starts at 0.6 mg once daily for one week and increases by 0.6 mg each week to the maintenance dose of 3 mg, delivered by a pen that dials 0.6, 1.2, 1.8, 2.4 or 3 mg ^[13]. If more than three days pass between doses, the label says to restart at 0.6 mg and repeat the escalation to limit gastrointestinal effects ^[13]. For diabetes, Victoza is used at 1.2 mg or 1.8 mg daily. The trial doses match the labels: 3.0 mg in SCALE ^{[4] [5] [6] [9]}, 1.8 mg as the lower arm in SCALE Diabetes ^[6], and 1.2 to 3.0 mg in the phase 2 study ^[3].

These are the doses of licensed products used under prescription, reported here for information. They are not a liraglutide dosage chart for research material, because a research vial has not been shown to contain what the label states and there is no pen to meter it. The licensed pens deliver fixed doses from a 6 mg/mL solution; someone reconstituting powder has none of that assurance. Our peptide calculator does the concentration arithmetic, and the bacteriostatic water guide covers the diluent, but neither substitutes for a licensed product.

Every licensed liraglutide product is a solution for subcutaneous injection in a prefilled pen, injected once daily in the abdomen, thigh or upper arm ^[13]. Research suppliers sell liraglutide as a freeze-dried powder, a form no trial has used. Liraglutide is not available as a tablet; the oral GLP-1 drugs are semaglutide and, in development, non-peptide molecules. Our news item on the oral semaglutide Wegovy pill covers the tablet route.

The liraglutide side effects listed on the Saxenda label as occurring in at least 5% of patients are nausea, diarrhoea, constipation, vomiting, injection-site reactions, headache, hypoglycaemia, dyspepsia, fatigue, dizziness, abdominal pain, raised lipase, upper abdominal pain, fever and gastroenteritis ^[13]. In SCALE Obesity, nausea affected 39% of the liraglutide group against 14% on placebo, and the most common reasons for stopping were vomiting and nausea, at 4.8% and 3.2% of liraglutide-treated patients ^[13]. Serious adverse events occurred in 6.2% on liraglutide against 5.0% on placebo in that trial ^[5].

The US label carries a boxed warning about thyroid C-cell tumours, based on rodent studies, and contraindicates liraglutide in people with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2. It also warns about acute pancreatitis, acute gallbladder disease, hypoglycaemia when used with insulin or sulfonylureas, kidney injury from dehydration, and suicidal behaviour and ideation, and advises monitoring for depression ^[13]. In the adolescent trial, one suicide occurred in the liraglutide group and was judged unlikely to be related to treatment ^[9].

In LEADER, the most common reason for stopping liraglutide was gastrointestinal events, and pancreatitis was non-significantly less common on liraglutide than on placebo ^[7]. These warnings and rates describe licensed products used under medical supervision. A vial from a research supplier carries the same pharmacology plus unknown content and purity, no pen, no label and no monitoring.

Liraglutide vs semaglutide has been tested directly. STEP 8, published in JAMA in 2022, randomised 338 adults with overweight or obesity and no diabetes to weekly semaglutide 2.4 mg or daily liraglutide 3.0 mg for 68 weeks. Weight fell by 15.8% on semaglutide against 6.4% on liraglutide, a difference of 9.4 percentage points, with placebo at 1.9% ^[11]. Semaglutide is more effective for weight loss and needs one injection a week instead of seven; liraglutide’s advantages are a longer safety record and, in the US, generic availability ^[15].

Cagrilintide, an amylin analogue, was also tested against liraglutide: in its phase 2 trial, cagrilintide 4.5 mg weekly produced 10.8% weight loss at 26 weeks against 9.0% on liraglutide 3.0 mg daily ^[16]. Tirzepatide and retatrutide have not been compared with liraglutide in obesity trials that we could find. Our tirzepatide vs semaglutide and retatrutide vs tirzepatide pages cover the newer comparisons, and peptides for weight loss gives an overview of the class.

Liraglutide is a licensed, prescription-only medicine. In the US, the label records an initial approval in 2010 for Victoza, and Saxenda is approved for chronic weight management in adults and in children aged 12 and over who meet the label’s BMI criteria ^[13]. In December 2024 the FDA approved the first generic liraglutide, referencing Victoza, from Hikma ^[15]. In the EU, Saxenda was authorised on 23 March 2015 for adults with a BMI of 30 or more, or 27 to 30 with a weight-related condition, and for adolescents aged 12 and over with obesity and a body weight above 60 kg ^[14]. Victoza is also authorised in the EU ^[14]. In the UK, both are prescription-only medicines regulated by the MHRA.

This changes how the law treats research-labelled liraglutide. In the UK, a product containing a prescription-only medicine can only be lawfully supplied against a prescription, whatever its label says; see the UK legal status page. In the US, the FDA has warned companies selling unapproved GLP-1 drugs labelled “for research purposes” that were in fact sold to consumers with dosing instructions ^[17]; see the US legal status page and our report on the FDA warnings to research-use GLP-1 sellers. The position in Europe, Canada and Australia is the same in substance: liraglutide is a prescription medicine, and a research vial is not a licensed product. Our legal status overview covers each country.

The Saxenda label says unused pens are stored in a refrigerator at 2 °C to 8 °C, must not be frozen, and after first use can be kept for 30 days at room temperature (15 °C to 30 °C) or in the refrigerator, with the cap on ^[13]. Those instructions apply to the licensed solution in its pen. Research material sold as a freeze-dried powder has no label; general practice is to keep it cold, dry and away from light and to refrigerate it once reconstituted. See how to store peptides.

The only lawful route to liraglutide as a medicine is a prescription for Victoza, Saxenda or a generic. PepFinder does not sell liraglutide. If you are comparing research suppliers, see compare liraglutide prices, read how to read a COA, and check our list of third-party tested suppliers. A certificate should report a measured mass consistent with the molecular weight of about 3751 g/mol and state the quantity in the vial.

We track listings in the UK, the US, Canada, Australia and Europe. Because generic liraglutide now exists, the price gap between a prescription and a research vial is smaller than for investigational peptides, which removes much of the reason anyone buys the latter. Our guides to third-party peptide testing, spotting a fake supplier and peptide prices explained cover what to check.