Who invented semaglutide, and how did it become a weight-loss medicine?

The discovery that set everything in motion

Picture a researcher in the late 1980s studying what happens in the gut after a meal. In 1987, scientists identified a hormone called glucagon-like peptide-1, abbreviated to GLP-1, that the intestine releases in response to food. It signals the pancreas to produce insulin, slows the stomach from emptying too quickly, and tells the brain that enough has been eaten. The natural hormone, though, breaks down in the bloodstream within minutes, far too fast to be a practical medicine.

That gap between biological promise and clinical usefulness is where years of chemistry came in. Researchers at Novo Nordisk spent the 1990s and early 2000s working out how to modify GLP-1 so it would survive long enough to act. Their first approved GLP-1 medicine, liraglutide, required a daily injection. The ambition was to go further: a once-weekly molecule. Semaglutide was the result. By attaching a long fatty-acid chain to the GLP-1 structure, Novo Nordisk's scientists gave it the ability to bind to albumin (a protein that circulates naturally in blood) and resist the enzymes that would otherwise degrade it. A weekly injection became possible. You can read more about how semaglutide works as a medicine if the mechanism interests you.

One misconception worth gently setting aside: semaglutide is sometimes described as a brand-new discovery, something that arrived from nowhere around 2021. In reality, the foundational science stretches back more than three decades, and the molecule itself was first described in published research around 2012.

How semaglutide moved from diabetes to weight management

Semaglutide first received regulatory approval as a diabetes medicine. In the UK it is still used for type 2 diabetes under the brand name Ozempic, at lower doses than those used for weight loss. The weight-management story began when clinical teams noticed that people taking GLP-1 medicines for diabetes were also losing meaningful amounts of weight, more than diet and exercise alone were likely to explain.

Novo Nordisk then ran a dedicated programme of weight-management trials called the STEP studies. The timeline of Wegovy's development covers this in more detail, but the short version is that the STEP 1 trial, published in the New England Journal of Medicine in 2021, showed an average body-weight reduction of around 15% over 68 weeks in adults with obesity who did not have diabetes, results that had not previously been seen from a medicine in this class. That evidence base supported approval of Wegovy, at a 2.4mg weekly maintenance dose, as a distinct product for weight management.

The UK regulator, the MHRA, licensed Wegovy for weight management. NICE then assessed it and in 2023 recommended semaglutide (TA875) for use within specialist weight management services, subject to a maximum treatment period of two years and BMI criteria. The NHS England page on weight management injections sets out the current NHS access criteria clearly.

What the inventors built, and where the medicine stands now

The Novo Nordisk team that developed semaglutide were not working on a weight-loss drug as such. They were trying to solve a problem in diabetes care, how to keep blood sugar stable between doses without asking patients to inject every day. The weight-management application followed from understanding the hormone system more completely. That is fairly common in medicine: a mechanism explored for one condition turns out to be relevant to another.

Since the original weekly injection, the semaglutide programme has continued. A higher 7.2mg weekly dose received MHRA approval in early 2026, with a dedicated single-dose pen approved in April 2026. More recently, in June 2026, the MHRA granted approval for the first oral semaglutide tablet for weight management in the UK, a once-daily formulation that reached the 25mg maintenance dose. The company behind semaglutide has described it as one of the most consequential medicines in its history, which, given Novo Nordisk's century-long record in metabolic disease, is a substantial claim.

For anyone thinking about what this history means in practical terms, the key point is that semaglutide is a well-characterised medicine with a long development trail, a substantial body of trial evidence, and clear regulatory oversight in the UK. It is not suitable for everyone, and a prescriber needs to assess the full picture before it can be prescribed. If you are wondering which pharmacies and services sell semaglutide, that is a sensible place to start before exploring whether it might be appropriate for you, and starting a free consultation is the practical next step.