Switching from Ozempic to Tirzepatide: what you need to know before you switch

Step 1: Understand what Ozempic is actually licensed for

Ozempic (semaglutide 0.5 mg, 1 mg and 2 mg) is licensed in the UK for type 2 diabetes management, not weight loss. The MHRA and NHS are clear on this distinction: the NHS medicines page for semaglutide sets out the separate indications for Ozempic (diabetes) and Wegovy (weight management), and conflating them is a common source of confusion.

If you have type 2 diabetes and your GP prescribed Ozempic, you are using it on-licence for that purpose. If someone sold or prescribed it to you primarily for weight loss without a diabetes diagnosis, that is an off-label use, and a responsible prescriber will want to understand that context before recommending any switch.

Understanding this distinction matters because the comparison you are really asking about is Ozempic's semaglutide against tirzepatide, and it is more useful to frame that as semaglutide at weight-loss doses versus tirzepatide, since the licensed weight-loss doses differ from Ozempic's diabetes doses. Get this framing right with your prescriber before anything else.

Step 2: Compare how the two medicines work and what the evidence says

Semaglutide is a GLP-1 receptor agonist: it mimics one gut hormone involved in appetite regulation and slows gastric emptying. Tirzepatide activates both GLP-1 and GIP receptors, which is why it is described as a dual agonist, the only one currently licensed for weight management in the UK.

In the SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025, tirzepatide produced greater average weight loss than semaglutide 2.4 mg over 72 weeks in adults with obesity and without diabetes. NICE's appraisal of tirzepatide (TA1026) notes that indirect comparisons also favour tirzepatide, though it is careful to acknowledge the uncertainty that comes with cross-trial comparisons.

The practical upshot: if you have been on Ozempic's diabetes doses (0.5–2 mg) and are now interested in weight management, the meaningful comparison is between Wegovy's maintenance dose (up to 2.4 mg, or 7.2 mg from early 2026) and Mounjaro's maintenance doses (up to 15 mg). You can explore the head-to-head differences between Wegovy and Mounjaro in more detail. The trial data consistently shows tirzepatide producing around 20–21% average body-weight reduction at 15 mg in SURMOUNT-1, versus roughly 15% with semaglutide 2.4 mg in STEP 1, though individual results vary and these were separate trials with different populations.

Step 3: What the switch process involves in practice

Switching is not a like-for-like product change. There is no validated conversion table that maps an Ozempic dose directly to a Mounjaro starting dose. In clinical practice, most prescribers restart at tirzepatide's 2.5 mg initiation dose (its job is to let your system adjust, not to deliver immediate therapeutic effect) and titrate upward from there based on your response and tolerability.

A full reassessment is standard. The prescriber will want to know your current indication, your dose history, any side effects you have experienced, your current weight and BMI, and any other medications you take. If you are considering switching from Ozempic to Mounjaro, our dedicated guide walks through what that process looks like and what your prescriber will typically want to discuss. For practical context on dose sequencing once a switch is agreed, our guide to tirzepatide dosing when switching from semaglutide covers the clinical rationale in detail.

One practical note worth mentioning: Mounjaro is a once-weekly subcutaneous injection delivered via a pre-filled KwikPen, most people keep it in the fridge door at home and inject on the same day each week. Storage details, including the exact room-temperature window allowed for travel, are in the Patient Information Leaflet and should be confirmed with your prescriber or pharmacist rather than estimated.

If your switch is from Wegovy specifically rather than Ozempic, the clinical picture is slightly different, and our page on when switching from semaglutide to tirzepatide covers the timing and dose considerations for that scenario. See also our page on switching from Wegovy to tirzepatide for that framing.

What IS licensed for weight loss in the UK, and how to access it

To be direct: if you are seeking weight management treatment, Ozempic is not the right starting point. The licensed options are Mounjaro (tirzepatide) and Wegovy (semaglutide as the weight-loss formulation), both are prescription-only medicines that require clinical assessment before a prescription can be issued.

At nume, a GPhC-registered Independent Prescriber reviews every consultation on the same day. There is no algorithm making that call. Our weight-loss treatment overview explains both options side by side, and you can read about how our clinical team approaches these decisions on our prescriber profile page. If you have questions before starting, our FAQs cover the most common ones.

Which medicine suits you is a clinical decision made with a prescriber, not a choice made by reading a comparison table. If you think tirzepatide might be the right next step, check your eligibility with our prescribers, it takes a few minutes and costs nothing.