Injectable GLP-1 weight loss treatment: making sense of your options

What the two licensed medicines actually do differently

The decision often starts here. Mounjaro (tirzepatide) is what clinicians call a dual agonist: it activates both the GIP and GLP-1 receptors involved in hunger signalling, insulin release and how fast the stomach empties. Wegovy (semaglutide) targets the GLP-1 receptor alone. That extra pathway matters in practice. In the SURMOUNT-1 trial (2,539 adults, 72 weeks) tirzepatide produced average weight reductions of around 20–21% at the highest dose, figures you can read in full in the original SURMOUNT-1 paper in the New England Journal of Medicine. The STEP 1 trial of semaglutide 2.4mg showed roughly 15% average reduction over 68 weeks. Both are meaningful clinical outcomes; neither is a guarantee for any individual.

A newer 7.2mg semaglutide pen was approved by the MHRA in April 2026, with trials reporting around 20.7% average loss, narrowing the gap with tirzepatide's highest dose considerably. So the landscape is shifting. Which medicine a prescriber recommends depends on your health history, any contraindications, and how you tolerate each starting dose.

If you want to understand how these medicines compare side by side, the GLP-1 weight loss injections overview covers the clinical comparison in more depth.

Who these treatments are licensed for, and what the prescriber actually weighs up

Both medicines are licensed for adults with a BMI of 30 or above, or a BMI of 27 or above alongside at least one weight-related health condition such as high blood pressure, type 2 diabetes, high cholesterol or obstructive sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. That said, BMI is a starting point, not a verdict. A prescriber looks at your full clinical picture: existing conditions, current medicines, any history of pancreatitis or thyroid conditions, and whether the medicine's risk profile fits your situation.

Some people are not suitable candidates. These medicines are not recommended during pregnancy, while breastfeeding, or if you are actively trying to conceive. They are not licensed for under-18s. Certain gastrointestinal conditions and a personal or family history of medullary thyroid carcinoma are among the contraindications that require careful prescriber discussion before anything is prescribed.

The approved weight loss injection page explains the UK licensing picture in more detail, including how NICE criteria differ from the private prescribing thresholds that apply at a registered pharmacy like ours.

The practical realities of injecting once a week

A question our prescribers hear regularly: is the injection itself difficult? Honestly, most people find the auto-injector pen less daunting than anticipated. The needle retracts automatically; the injection takes seconds. You rotate sites between your abdomen, thigh, and upper arm. You keep the pen in the fridge (2–8°C) and refer to your Patient Information Leaflet for the exact window it can be stored at room temperature if you need to travel. The injectable pen guide walks through what to expect physically from the first injection onward.

Side effects are worth planning for rather than worrying about. Nausea and loose stools are the most common, especially in the early weeks or after a dose step-up. They are generally mild to moderate and tend to settle as your body adjusts. The NHS tirzepatide medicines page lists the full side-effect profile for Mounjaro; the equivalent semaglutide page covers Wegovy. Eating smaller, lower-fat meals (particularly around injection day) helps many people. Staying well hydrated matters too.

One practical note on timing: if you order by midday on a weekday, a GPhC-registered prescriber at our pharmacy reviews your consultation the same day, and treatment dispatches the same afternoon for next-working-day delivery. That's the cut-off worth knowing if you're planning around a busy week. Aftercare is available seven days a week, which is useful when a new dose lands and questions come up at the weekend.

For a broader look at what living with injectable treatment involves week to week, the injectable weight loss treatment guide is a useful next read.

How to approach the cost question sensibly

Price is a reasonable thing to think about for a treatment you may be taking for months. Since Eli Lilly raised Mounjaro's UK list price in September 2025, private prices for injectable GLP-1 treatment have typically ranged from around £149 to £375 per month depending on the dose and provider, figures that have been widely reported. If you're weighing up your options, our weight loss injection treatment page gives a clear overview of what is available and how each option is structured before you look at costs in detail. The cost breakdown for weight loss injections explains what that range reflects and what headline prices sometimes leave out (consultation fees, prescription charges, delivery costs, aftercare).

At nume, one transparent price covers the clinical consultation, the prescription, the medicine itself, free next-working-day tracked delivery, and access to prescriber-led aftercare seven days a week. No subscription. Every repeat order is clinically reviewed before it ships. We are not trying to be the cheapest option on the market. For a prescription medicine that requires genuine clinical oversight and a verified supply chain, price is the wrong test to lead with. The right questions are: is this pharmacy on the GPhC register, is a qualified prescriber reviewing my case, and is the medicine coming through the authorised UK supply chain? You can check any pharmacy's registration at the GPhC pharmacy register. Ours is listed under registration number 9012878.

When you feel ready to check whether you're clinically suitable, the free consultation page is the place to start.