The history of semaglutide: how a lizard's saliva became a weight-loss medicine

It started with a lizard, then forty years of endocrinology

In the early 1980s, scientists studying the Gila monster (a large venomous lizard native to the American Southwest) noticed it could go months between meals without losing meaningful muscle mass. A peptide in its saliva turned out to activate the same receptor that a human gut hormone called GLP-1 (glucagon-like peptide-1) activates after eating. GLP-1 tells the pancreas to release insulin, slows digestion, and signals the brain that you've had enough food.

The problem with natural GLP-1 is that the body breaks it down within minutes. The pharmacological challenge, from the late 1980s through the 2000s, was building a molecule that behaved like GLP-1 but lasted long enough to be clinically useful. Exenatide (twice-daily injection) came first. Liraglutide, which lasts 24 hours, followed. Novo Nordisk's next move was to create a version with a fatty acid chain that binds to albumin in the bloodstream, extending the half-life to about a week. That molecule is semaglutide.

The weekly injection became Ozempic, approved in the UK for type 2 diabetes. Crucially, the semaglutide overview on this site covers that licensing distinction in detail, Ozempic remains a diabetes medicine, and using it for weight loss outside a licensed indication isn't what this history leads to.

The Wegovy chapter: what changed when the dose went up

While Ozempic was making its way into diabetes clinics, researchers noticed something consistent in trial data: patients lost weight. The question was whether a higher, dedicated dose could be developed and proven specifically for obesity. The answer came from the STEP programme, a series of large randomised trials. STEP 1, published in the New England Journal of Medicine in 2021, randomised around 1,900 adults with obesity (without diabetes) to semaglutide 2.4 mg weekly or placebo alongside lifestyle support. Average weight loss over 68 weeks was roughly 15% of body weight, a result that shifted the conversation about what medicines could achieve in obesity treatment.

The UK's Medicines and Healthcare products Regulatory Agency licensed Wegovy for weight management on that evidence. NICE subsequently recommended it under specific conditions, which you can read in detail on the Wegovy treatment page. The NHS recommendation comes with a two-year maximum and a requirement for specialist multidisciplinary support, which is why private routes remain relevant for many people who don't meet the NHS threshold or prefer not to wait.

If you want to go deeper on the full Wegovy story, including the supply shortages that complicated its UK rollout, that page covers it.

The past eighteen months have moved quickly

The semaglutide timeline didn't pause after the 2.4 mg weekly pen was approved. In January 2026 the MHRA approved a higher 7.2 mg maintenance dose, initially delivered as three 2.4 mg pens weekly. Then, on 14 April 2026, the MHRA approved a dedicated single-dose 7.2 mg pen (one injection a week, auto-dosing, covered needle, locks after use) for adults with a BMI of 30 or above. Trials at this dose reported average weight loss of around 20.7% over 72 weeks, closing the gap with tirzepatide results seen in recent head-to-head data.

June 2026 brought another milestone. The MHRA approved an oral semaglutide tablet (co-formulated with an absorption enhancer called SNAC) as the first oral GLP-1 medicine licensed for weight management in the UK, making the UK the first in Europe to receive it. The tablet uses a 1.5 mg starting dose, titrated monthly up to a 25 mg maintenance dose. It's taken first thing in the morning on an empty stomach, with a small amount of plain water, at least 30 minutes before food or other medicines, and unlike the injection, it needs no refrigeration. For people nervous about injections, that timing detail (before the kettle goes on, before Monday's inbox opens) is often the practical point that tips the decision.

The MHRA also approved Wegovy for a separate indication in July 2026: treatment of MASH, a form of fatty liver disease in adults with moderate-to-advanced fibrosis. That extension of the licence reflects how the evidence base for semaglutide has continued to grow well beyond its origins in appetite signalling. For current UK weight-loss treatment options, this developing picture matters.

Where the history leaves you now

Understanding this background helps make sense of why the prescribing conversation is more nuanced than a simple dose recommendation. Semaglutide arrived in the UK through diabetes licensing, expanded via a dedicated obesity programme, and is now available in injection and tablet form at doses that didn't exist two years ago. The science supports using it; the licensing specifies exactly who it's approved for and how; and a GPhC-registered prescriber reviews all of those details before any prescription is issued.

At nume, every consultation is read the same day by a named, GPhC-registered Independent Prescriber (a real clinician, not software) who can discuss which licensed option fits your circumstances. The semaglutide 0.5 mg dose page and the 1 mg dose page cover the titration schedule in factual detail, and the NHS's own patient information for semaglutide is the right reference for side effects, storage and the full patient leaflet. The STEP 1 trial data, published in the New England Journal of Medicine, underpins the licensed dose's effectiveness. If you're considering treatment, the consultation comes first.