What hormone is in Wegovy — and what does it actually do?

Where GLP-1 comes from, and why its natural version barely lasts two minutes

GLP-1 is secreted by L-cells lining the lower part of your small intestine. The trigger is food arriving in the gut, particularly carbohydrates and fats. Once released, GLP-1 travels through the bloodstream to act on the brain's appetite centres, the pancreas and the stomach lining simultaneously. The brain receives a satiety signal; the pancreas adjusts insulin secretion in response to glucose; the stomach slows its emptying so food lingers longer and you feel fuller for longer after meals.

Here is the catch with natural GLP-1: an enzyme called dipeptidyl peptidase-4 (DPP-4) degrades it almost immediately, so its active lifespan in the blood is typically under two minutes. Your body produces it, but it disappears before it can do sustained work. This is relevant to understanding how semaglutide affects hormone levels differently from what the body manages on its own.

Novo Nordisk's solution was to engineer a molecule that is structurally similar enough to human GLP-1 to bind the same receptor, but chemically modified to evade DPP-4 and to attach loosely to albumin in the blood. That attachment acts like a slow-release reservoir. The result is a molecule with a half-life of roughly seven days, precise enough to support once-weekly dosing. The NHS patient information page for semaglutide describes the mechanism in plain terms and is worth bookmarking for reference throughout treatment.

What the GLP-1 receptor actually does when semaglutide binds to it

The GLP-1 receptor sits on cells in several tissues, the hypothalamus, the brainstem, the stomach wall, the pancreatic beta cells and elsewhere. Semaglutide binds to all of these with high affinity. In practical terms, three things happen that are directly relevant to weight.

First, appetite is blunted at a neurological level. The hypothalamus receives a prolonged satiety signal, which is why many people find they feel full more quickly than before treatment and think about food less between meals. Second, gastric emptying slows: food moves from the stomach to the small intestine more gradually, extending the feeling of fullness after eating. Third, blood glucose responses are moderated because insulin secretion is enhanced in the presence of elevated glucose and glucagon release is partially suppressed, though the weight-management mechanism is distinct from the diabetes mechanism.

None of this is a willpower boost. The biology is being altered at a receptor level. That framing matters: weight is shaped by hormonal physiology, not character. Whether Wegovy changes your wider hormone profile is a question worth exploring separately, particularly for anyone also managing thyroid conditions or reproductive hormones.

The trial evidence behind Wegovy's GLP-1 mechanism, what 68 weeks of data showed

The STEP 1 trial enrolled 1,961 adults with obesity or overweight and at least one weight-related condition, and randomised them to once-weekly semaglutide 2.4 mg or placebo alongside lifestyle support. After 68 weeks, the semaglutide group had achieved a mean weight reduction of around 15%, compared with around 2.4% in the placebo group. That gap is large by the standards of pharmaceutical weight management, and regulators on both sides of the Atlantic found it persuasive. The NICE technology appraisal for semaglutide (TA875) reviewed this evidence before recommending it for NHS use within specialist weight management services. It is worth noting that the NICE recommendation comes with a two-year treatment limit and conditions around specialist oversight, so accessing Wegovy on the NHS is not straightforward for most people.

If you are thinking through your options and wondering what private treatment actually costs, the treatment overview page sets out what is included in a private consultation and what the process involves. A prescriber at a GPhC-registered pharmacy reviews your information in full before any medicine is issued, there is no shortcut around that clinical step, and nor should there be.

It is completely natural to feel uncertain when reading about hormones and biological mechanisms; a lot of the language in this area gets technical fast. The honest summary is simpler: Wegovy works by amplifying a signal your gut already makes, using a hormone your body already recognises. The synthetic version just stays long enough to make a sustained difference. Our full semaglutide resource covers the wider clinical picture if you want to go deeper.

How Wegovy's single GLP-1 pathway compares with dual-agonist treatment

Understanding which medication Wegovy actually is also helps clarify what it does not contain. Wegovy targets the GLP-1 receptor alone. Tirzepatide, the active ingredient in Mounjaro, targets both GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors simultaneously, making it the only dual-agonist weight-loss medicine currently licensed in the UK. GIP is another gut hormone involved in fat storage and energy metabolism, and activating both receptors together appears to produce somewhat greater average weight reductions than GLP-1 activation alone, based on head-to-head trial data. Whether a single or dual pathway is appropriate is a clinical question rather than a simple better-or-worse judgment.

Wegovy is also the active ingredient in Ozempic, but the two brands are licensed for different purposes: Ozempic for type 2 diabetes, Wegovy for weight management. The same molecule, but different licensed doses and indications. Conflating them is a common source of confusion online, and if you have ever wondered whether Wegovy contains hormones, that question is worth reading through before speaking to a prescriber. For a fuller comparison of the medicines available through num, the weight-loss treatment overview is the clearest starting point before you speak to a prescriber.