Wegovy composition: what the injection actually contains

The active ingredient: semaglutide and how it is made to last

Semaglutide is the substance doing the clinical work in Wegovy. It is a synthetic analogue of glucagon-like peptide-1, commonly written as GLP-1 — a hormone released by cells in your small intestine when you eat. The natural hormone is broken down by the body within minutes; semaglutide has been chemically altered so that it stays active for around seven days, which is why one injection a week is enough.

The modification involves attaching a fatty-acid chain to the semaglutide molecule via a linker. That chain binds loosely to albumin, a protein that circulates in the blood, which slows the body's enzymes from clearing it. The result is a medicine with a half-life of roughly one week. None of this changes what semaglutide does, it still activates the same GLP-1 receptors in the brain and gut that the natural hormone activates, signalling fullness and slowing the rate at which food leaves the stomach. The NHS patient information on semaglutide gives a readable overview of how the medicine works and what to expect.

For a more detailed look at what people notice in practice once treatment is under way, you can read what patients who have had a positive experience with Wegovy say about it, alongside the positive effects reported with Wegovy page, which covers the clinical evidence alongside real-world experience.

What the excipients are, and what they are not

Beyond semaglutide, the injection solution contains a small number of inactive ingredients, known in pharmacy as excipients. These appear in full in the Summary of Product Characteristics published on the Electronic Medicines Compendium (eMC), which holds the Wegovy SmPC for the UK.

The excipients in the Wegovy subcutaneous solution typically include disodium phosphate dihydrate and sodium chloride as buffering and tonicity agents, hydrochloric acid or sodium hydroxide to adjust pH, and water for injections as the solvent. That is broadly it. There is no insulin, no stimulant, no hormone other than the semaglutide analogue, and no animal-derived ingredient in the active formulation. The solution is clear to slightly yellow, a colour variation that is normal and does not mean anything is wrong with the pen.

People sometimes worry that because these medicines affect appetite so strongly they must contain something more exotic. They do not. The effect comes from the receptor pharmacology of semaglutide itself, not from any additional active substance. If you are curious about how the wider components of Wegovy interact, that page goes into more depth on the excipient list and what each one does.

Dose strengths and the titration sequence

Composition also includes knowing which strength is in the pen you are holding. Wegovy is supplied in five dose strengths: 0.25 mg, 0.5 mg, 1.0 mg, 1.7 mg, and 2.4 mg per dose. A newer 7.2 mg maintenance dose received MHRA approval in early 2026, initially delivered as three 2.4 mg pens per week and more recently as a dedicated single-dose pen approved on 14 April 2026.

Treatment begins at 0.25 mg, a dose whose job is to allow your digestive system to adjust, not to drive significant weight loss. The prescriber steps the dose up roughly every four weeks. Most people reach and stay at 2.4 mg, the standard maintenance dose. The concentration of semaglutide in the solution differs by pen; the excipient blend stays the same across strengths.

This matters for a practical reason: if you are thinking about switching from another injectable treatment, the titration sequence and semaglutide's specific formulation both affect how the transition works. The guidance on moving from Saxenda to Wegovy covers what that switch involves clinically. And if cost is part of your thinking, the Wegovy cost context page explains how private pricing in the UK is structured, a useful read before your consultation, particularly if you are planning to start around a specific month when budgeting feels tighter.

Who makes Wegovy and what the UK licence covers

Wegovy is manufactured by Novo Nordisk, a Danish pharmaceutical company whose UK operations supply the pens through the licensed UK supply chain. Understanding who stands behind a medicine matters when you are deciding where to obtain it. Counterfeit weight-loss pens have been seized in significant numbers by the MHRA, fake products that have in some cases contained insulin rather than the stated ingredient. The only safe route to Wegovy is through a pharmacy you can verify on the GPhC pharmacy register, following a legitimate clinical assessment.

The UK licence covers adults with a BMI of 30 or above, or 27 or above alongside a weight-related health condition such as high blood pressure, high cholesterol, or type 2 diabetes. It does not cover use in pregnancy, breastfeeding, or in under-18s. Novo Nordisk's background and the development of the medicine are covered on the Wegovy manufacturer page if you want the broader context.

Once you have a clear picture of what the medicine contains and whether it is appropriate for your circumstances, the natural next step is a clinical conversation. At nume, a GPhC-registered prescriber reviews every consultation personally before anything is dispensed. Check your eligibility and start your free consultation to find out whether Wegovy is the right option for you.