Is Ozempic semaglutide or tirzepatide? What the active ingredient actually is

What is the active ingredient in Ozempic, and how does it work?

Ozempic contains semaglutide. It works by mimicking GLP-1, a gut hormone released after eating that signals fullness to the brain, slows the rate at which the stomach empties, and helps regulate blood sugar. Novo Nordisk developed semaglutide originally as a diabetes treatment, and Ozempic's UK licence reflects that: it is approved for managing type 2 diabetes in adults, not for weight management. The NHS medicines page for semaglutide sets this out plainly and is worth a quick read if you want the patient-level summary.

The word "tirzepatide" sometimes gets attached to Ozempic in search queries because the two medicines are in the same drug class and share a similar injection-pen format. They are not the same molecule. Tirzepatide, sold as Mounjaro, targets two receptors simultaneously (GLP-1 and GIP) which is why it is described as a dual agonist. Semaglutide targets GLP-1 only. That mechanistic difference is one reason their clinical trial results and prescribing considerations vary. You can read a fuller breakdown on the semaglutide explained page.

One quick way to check any medicine's active ingredient: look at the PIL (patient information leaflet) inside the pack, or search the brand name on the Electronic Medicines Compendium (eMC), which holds every UK-licensed medicine's full summary of product characteristics. Takes under a minute.

So which semaglutide brand is actually licensed for weight loss in the UK?

Two of them, both called Wegovy. The original Wegovy is a once-weekly subcutaneous injection, starting at 0.25 mg and titrated by a prescriber up to a 2.4 mg maintenance dose, with a higher 7.2 mg dose now also approved by the MHRA. The second is Wegovy tablets, oral semaglutide, approved by the MHRA on 11 June 2026, making it the first oral GLP-1 medicine licensed for weight management in the UK. The tablet schedule runs from 1.5 mg daily up to a 25 mg maintenance dose, again under prescriber supervision. Both are licensed for adults with a BMI of 30 or above, or 27 or above alongside at least one weight-related condition.

Ozempic is not interchangeable with Wegovy for weight loss, even though both contain semaglutide. The doses differ, the formulations differ, and using one medicine off-label in place of another is a clinical decision that belongs with a prescriber, not with the person searching online. The MHRA has been explicit that GLP-1 medicines are not assessed or licensed for quick or cosmetic weight loss. Our guide comparing Wegovy and Ozempic goes into the licence distinction in more detail.

If you are weighing up cost alongside efficacy, the Wegovy cost page covers what UK private treatment typically involves financially, including what a legitimate price should include beyond the medicine itself.

What is tirzepatide, and how does it differ from semaglutide in practice?

Tirzepatide (Mounjaro) is a different active ingredient altogether. Where semaglutide acts on one receptor pathway, tirzepatide activates both GLP-1 and GIP receptors, the latter being involved in insulin secretion and fat metabolism. The SURMOUNT-1 trial, published in the New England Journal of Medicine, reported an average body-weight reduction of around 20–21% at the highest dose over 72 weeks in adults with obesity. The SURMOUNT-5 trial, also published in the NEJM in 2025, compared tirzepatide head-to-head against semaglutide 2.4 mg and found tirzepatide produced greater average weight reduction over 72 weeks. NICE recommended tirzepatide for NHS use in December 2024 (guidance TA1026), subject to eligibility criteria that include BMI thresholds and weight-related comorbidities.

That trial evidence does not mean tirzepatide is the right choice for every person. Side-effect profiles overlap substantially (both medicines share a GI-led pattern of nausea, diarrhoea and constipation, particularly in the early weeks) but individual tolerance, medical history and other medicines all shape what a prescriber recommends. The semaglutide explained page and the Wegovy overview cover the respective profiles in plain terms.

Which weight-loss medicines are actually licensed in the UK, and how do you access them?

The two prescription weight-loss injections currently licensed in the UK are Wegovy (semaglutide, Novo Nordisk) and Mounjaro (tirzepatide, Eli Lilly). Wegovy tablets joined them in June 2026. Ozempic is not on that list. Saxenda (liraglutide) holds a weight-management licence but is a separate medicine and not dispensed by nume. Orlistat is available for weight management at lower doses over the counter and by prescription at higher doses.

If you want to explore whether Wegovy or Mounjaro might be suitable for you, the starting point is a clinical consultation. At nume, a GPhC-registered Independent Prescriber reads every consultation personally on the day it comes in. There is no algorithm making that call. Our weight-loss treatment overview sets out what the process involves, and you can see details of our clinical team on the clinical team page. If you have questions before you start, the FAQs cover the most common ones. When you are ready, speak to our prescribers through a free consultation.