What are the active ingredients in Wegovy?

The active ingredient is semaglutide. Everything else listed with the medicine are excipients — formulation components that stabilise the solution and help the injection work properly — but they do not contribute therapeutic activity. When people talk about Wegovy’s effect, they’re talking about semaglutide acting on GLP-1 receptors.

Why semaglutide matters

Semaglutide is the single therapeutic component in Wegovy. It belongs to a class of medicines called GLP-1 receptor agonists, which mimic the action of the body’s natural hormone GLP-1. By activating these receptors, semaglutide helps regulate appetite, making it easier for people to feel satisfied with smaller meals. NICE guidance emphasises that this mechanism is the foundation of Wegovy’s effectiveness, with trial participants losing on average between 10% and 15% of their starting weight over a year. These results would not be possible without the specific action of semaglutide on appetite-control centres in the brain.

The role of excipients

Alongside semaglutide, Wegovy contains a small set of inactive ingredients, often referred to as excipients. These include substances such as water for injection and stabilisers that help preserve the medicine in its pre-filled pen. Their role is purely practical: ensuring that the active ingredient remains stable, safe, and effective until it is administered. They do not play any part in the appetite-regulating effects or weight-loss outcomes. NHS information makes clear that when people speak about the impact of Wegovy, it is semaglutide alone that is responsible.

How semaglutide was developed

Semaglutide did not appear overnight. It was first developed for managing type 2 diabetes, where it proved effective at improving blood sugar control. Researchers then observed that many participants experienced significant weight loss. This prompted dedicated trials in people living with excess weight but without diabetes, eventually leading to Wegovy’s approval for weight management. The UK’s NICE appraisal reflected on this pathway, noting that the evidence base is extensive, covering both metabolic and weight outcomes. This background explains why semaglutide has become central to modern discussions about medical support for weight management.

Evidence behind its effects

Clinical studies demonstrate that semaglutide’s effect on appetite and digestion leads to sustained reductions in calorie intake. Participants using the medicine consumed fewer calories at meals, reported less hunger between meals, and found cravings easier to manage. Over time, these changes produced average weight losses of around 15% when combined with structured support. NHS England has acknowledged these results, estimating that treatments like Wegovy could significantly reduce long-term health risks associated with excess weight. For many, the key point is that this outcome is due to semaglutide alone, not to the excipients or any other part of the formulation.

Benefits beyond weight reduction

While weight loss is the most visible effect, semaglutide has also shown benefits for wider health. Trials have reported improvements in blood pressure, cholesterol, and blood sugar levels. In 2024, the UK regulator extended semaglutide’s licence to include reducing the risk of cardiovascular events in adults with heart disease and a body-mass index of 27 or more. This decision was based on evidence showing roughly a 20% reduction in heart attacks and strokes among people treated with semaglutide compared with placebo. Again, these benefits are attributable to semaglutide itself, underscoring its role as the sole active ingredient in Wegovy.

What this means in practice

Wegovy’s impact rests entirely on semaglutide, the medicine’s active ingredient. The other listed components are there only to keep the solution safe and stable for use in pre-filled injection pens. Clinical evidence from NICE and NHS evaluations confirms that semaglutide reduces appetite, supports average weight reductions of 10–15% over a year, and improves key health markers. For people prescribed Wegovy, it is helpful to know that the benefits they may experience — from reduced food cravings to lower cardiovascular risk — come from the action of semaglutide on GLP-1 receptors, not from anything else in the formulation.