The generic names behind weight loss injections — and why they matter

You've seen 'Mounjaro' and 'Wegovy' everywhere, here's the actual pharmacology

Picture the moment you first see a prescription: the prescriber writes tirzepatide 2.5 mg, not Mounjaro. That is the generic name doing its job, identifying the active molecule precisely, regardless of who manufactures it or what the box says. Tirzepatide activates two gut-hormone receptors simultaneously, GIP and GLP-1, which together reduce appetite and slow gastric emptying. No other weight-loss injection licensed in the UK works this way. Semaglutide, on the other hand, targets the GLP-1 receptor alone, a single pathway, still highly effective, and the basis of Wegovy's trial results.

Knowing the generic name lets you read the clinical evidence directly. The SURMOUNT-1 trial, for example, is filed under tirzepatide in every database; the New England Journal of Medicine publication uses that name throughout. When a headline says a new study looked at semaglutide, you know it applies to every semaglutide product, not just one brand.

There is a practical implication for safety too. Semaglutide appears under at least three UK brand names: Wegovy (weight management injection), Ozempic (type 2 diabetes), and, as of June 2026, Wegovy tablets. If you are ever transferred between brands or products, your prescriber needs to know which semaglutide formulation and dose you have been on. If you are still piecing together what the names of weight loss injections actually refer to, it matters more than most people realise at the start of treatment.

Ozempic, Saxenda, Rybelsus, generic names that clarify what is and is not licensed for weight loss

This is where generic names save people from genuine confusion, and sometimes from real risk. Ozempic's generic name is semaglutide, but its UK licence is for type 2 diabetes management, not weight loss. The dose and the regulatory intent are different from Wegovy. Prescribing Ozempic for weight loss in someone without diabetes is off-label, and it is not what a regulated UK weight-management service will offer you.

Saxenda's generic name is liraglutide, a first-generation GLP-1 receptor agonist administered daily rather than weekly. It was licensed for weight management before semaglutide arrived; it is less commonly prescribed now given the stronger evidence base and more convenient dosing schedules of the newer medicines. Rybelsus is oral semaglutide at 3, 7 or 14 mg, licensed for type 2 diabetes only. The Wegovy tablet (1.5 mg to 25 mg) is a completely separate product with its own weight-management licence, approved by the MHRA in June 2026.

The NHS tirzepatide information page and its semaglutide counterpart set out the licensed indications clearly. If a seller is offering you a named medicine without any discussion of its actual licence, that is worth pausing over. You can read more about what a thorough clinical assessment looks like on our weight loss injections overview.

What the generic name does not tell you, and where clinical review fills the gap

Knowing that tirzepatide exists, or that semaglutide has a stronger long-term evidence base than earlier options, does not tell you which of them suits you specifically. That depends on your weight-related health conditions, any medicines you already take, your history with GI problems, whether you are using oral contraception (tirzepatide can reduce pill absorption in the first weeks of each dose increase, so an additional method is advised), and a range of factors a prescriber weighs up in a proper consultation. If you want a clear picture of what the different weight loss injections are called and how those names relate to one another, that is useful groundwork to cover before your consultation.

Both medicines carry contraindications. Neither is recommended during pregnancy, breastfeeding, or for anyone trying to conceive. Under-18s are outside the licensed indications entirely. A personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2 requires direct prescriber discussion before either medicine is started.

At nume, a GPhC-registered Independent Prescriber reads every consultation personally, a real clinician, not a scoring algorithm. If approved, the pen is dispatched the same day (for orders in before 12pm on a working day) and arrives via DPD the next working day in plain, unbranded packaging. The tracking notification on your phone is often the first sign that the clinical decision has been made. For context on what private treatment costs and what is included, the treatment overview page sets it out plainly. If tiredness after starting is something you are wondering about, fatigue is one of the questions our prescribers hear regularly.

The generic name on your prescription is the same molecule that was studied in the clinical trials, reviewed by NICE, and approved by the MHRA, and for those exploring unbranded options, our guide to weight loss injections available in generic form explains what that means in practice. Our clinical team is built around exactly that chain.