What does Wegovy have in it, and what does that mean for you?

The active ingredient: semaglutide and the GLP-1 connection

Semaglutide is the heart of Wegovy. It is a GLP-1 receptor agonist, a molecule engineered to behave like glucagon-like peptide-1, one of the hormones your gut releases in the minutes after you eat. The natural version is cleared from your bloodstream within minutes. Semaglutide is designed differently: a fatty acid chain tethers it to a blood protein called albumin, slowing its breakdown dramatically and allowing a single weekly injection to sustain that hormone signal around the clock.

What that signal does is worth understanding clearly. GLP-1 receptors sit in several places, the pancreas, the brain's appetite centres, and the stomach wall. When semaglutide binds to them, it prompts the pancreas to release insulin in response to food, slows the rate at which the stomach empties, and sends satiety signals to the brain. You feel full sooner, stay full longer, and tend to eat less without forcing it. That biological mechanism is distinct from willpower; it is a pharmacological shift in how hunger is regulated.

For the injection, the drug is delivered as a sterile aqueous solution. It uses a pre-filled auto-injector pen administered under the skin once a week. You can read more about the ingredient itself on the semaglutide overview page, which covers its licensed uses across both weight management and type 2 diabetes.

What else is in the pen: the inactive ingredients

Beyond semaglutide itself, the Wegovy injection solution contains a small set of excipients. These are standard pharmaceutical substances chosen to keep the medicine chemically stable, at the correct acidity for subcutaneous injection, and free from contamination across its shelf life. The full ingredient list (including the exact preservative, buffer and tonicity agent used) is published in the Wegovy Summary of Product Characteristics on the electronic Medicines Compendium (eMC), which is the reference source your prescriber and pharmacist use. If you have a known allergy to any pharmaceutical excipient, that is something to raise at your consultation before treatment is prescribed.

Storage matters here. The inactive ingredients help keep semaglutide stable under refrigeration (2–8°C), but the SmPC specifies a limited window during which a pen may be kept at room temperature. The exact duration is in the Patient Information Leaflet, worth reading before your first pen goes in the fridge door next to the milk, rather than discovering later that it sat on the counter too long.

The pen doses are fixed: Wegovy follows a titration schedule from 0.25mg up to a 2.4mg maintenance dose, with each strength supplied as a separate pre-filled pen. A newer 7.2mg single-dose pen received MHRA approval in April 2026 for adults with a BMI of 30 or above. The full dose range page covers each pen format in detail, and what Wegovy goes up to explains the maximum licensed dose.

The oral tablet: a different formulation, the same active ingredient

In June 2026 the MHRA approved Wegovy tablets, making the UK the first country in Europe to license an oral GLP-1 medicine for weight management. The active ingredient is still semaglutide, but the formulation challenge here is significant: semaglutide is a large peptide molecule that digestive enzymes would ordinarily destroy before it reaches the bloodstream. The tablet overcomes this by combining semaglutide with an absorption enhancer called sodium N-(8-[2-hydroxybenzoyl] amino) caprylate, SNAC for short. SNAC briefly raises the local pH of the stomach lining around the tablet, allowing semaglutide to absorb through it intact.

This matters for how the tablet must be taken: first thing in the morning, on an empty stomach, with a small amount of plain water, and nothing else (no food, coffee or other medicines) for at least 30 minutes after. Oral bioavailability is lower than the injection, and the titration reflects that, moving from 1.5mg through 4mg and 9mg to a 25mg maintenance dose. Trial data from the OASIS 4 study reported an average weight loss of around 13.6% over 64 weeks, rising to roughly 17% among participants who adhered fully to treatment. The tablet requires no refrigeration, which makes it the more travel-friendly format. Wegovy tablets are a private prescription only at launch, no NICE appraisal has taken place yet. The Wegovy overview page sets out both formats side by side.

Does it matter that Wegovy only targets GLP-1, not GIP?

This is a question our prescribers hear fairly regularly. Wegovy acts on GLP-1 receptors only. A separate class of medicine (tirzepatide, sold as Mounjaro) activates both GLP-1 and GIP receptors, making it a dual-agonist. Clinical trial evidence, including the SURMOUNT-5 head-to-head study published in the New England Journal of Medicine in 2025, found that tirzepatide produced greater average weight reduction than semaglutide 2.4mg over 72 weeks. Whether that difference is clinically meaningful for a given individual depends on factors a prescriber weighs at consultation: your medical history, any contraindications, which formulation suits your routine, and cost.

Wegovy's GLP-1 mechanism is thoroughly evidenced. The STEP 1 trial, also published in the New England Journal of Medicine, reported an average body-weight reduction of around 15% over 68 weeks at the 2.4mg maintenance dose, among adults with obesity and no diabetes. That is a meaningful result. Which option fits your situation is a clinical decision, not one to make on ingredient lists alone. The weight-loss treatment overview gives a balanced picture of the options licensed in the UK, and Wegovy's cost context covers what private treatment realistically involves.

If you are ready to talk through whether Wegovy (or another licensed treatment) is right for you, our prescribers are available seven days a week. Check your eligibility with a free consultation, reviewed the same day by a real clinician.