What types of weight loss injection are available in the UK?

You've heard about 'weight loss jabs', here's what that actually means

The phrase gets used loosely online, which can make it hard to know what you're actually looking at. In the UK, there are two injections with a full product licence for weight management in adults: Mounjaro (tirzepatide, made by Eli Lilly) and Wegovy (semaglutide, made by Novo Nordisk). Both sit in the GLP-1 class of medicines, though they work through slightly different mechanisms, more on that below.

A few medicines you'll come across in conversation don't belong in this list. Ozempic is also semaglutide, but it is licensed for type 2 diabetes, not weight management. Saxenda (liraglutide) holds a UK weight-management licence but is a daily injection and is used far less frequently since the weekly options arrived. Neither Ozempic nor Saxenda is dispensed by our pharmacy; we focus on the two medicines with the strongest current evidence and widest clinical use. If you want to understand how these options compare, you can read about what other weight loss injections exist beyond the two we supply, which sets out the full picture in plain terms.

Counterfeits are a genuine concern. The MHRA has issued repeated warnings about fake pens sold through social media and unverified websites, some containing insulin rather than the stated medicine. Any legitimate supply requires a prescription issued after a proper clinical assessment, and the MHRA's Yellow Card scheme is the place to report anything suspicious.

How each injection works, and why the difference matters

Semaglutide mimics GLP-1, a gut hormone released after eating. By binding to GLP-1 receptors, it slows the movement of food through the stomach, signals fullness to the brain, and reduces the urge to eat between meals. The STEP 1 trial, published in the New England Journal of Medicine, recorded an average body-weight reduction of around 15% over 68 weeks at the 2.4mg maintenance dose. That's a meaningful result by any clinical measure.

Tirzepatide goes a step further. It activates both GLP-1 and GIP receptors simultaneously, GIP being a second gut hormone involved in appetite regulation and energy metabolism. This dual action is why tirzepatide sits apart from every other licensed weight-management injection in the UK, and it also explains why people often ask about what types of weight loss injections are there once they learn the mechanisms differ. In the SURMOUNT-1 trial (2,539 participants, 72 weeks), the 15mg dose produced an average weight reduction of around 20–21%. In the later SURMOUNT-5 head-to-head study, tirzepatide produced greater average weight loss than semaglutide 2.4mg directly compared, as noted in NICE's appraisal of tirzepatide (TA1026).

That said, which injection is right for a specific person depends on more than trial averages. Tolerability, existing health conditions, other medicines, and clinical history all feed into the prescriber's assessment. The numbers are context, not a prescription.

Who each injection is licensed for, and where the dose schedules sit

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 condition such as high blood pressure, raised cholesterol, obstructive sleep apnoea, prediabetes or type 2 diabetes. Lower BMI thresholds can apply for some ethnic backgrounds under UK guidance.

The titration approach is similar for both. Mounjaro starts at 2.5mg (a dose whose job is to let your system adjust rather than to drive immediate weight loss) and moves upward, typically in four-week steps, through six strengths up to 15mg. Wegovy begins at 0.25mg and steps up through four stages to 2.4mg, with a higher 7.2mg dose now also approved. For a closer look at how the schedules and formulations differ, our overview of each type of weight loss injection walks through the practical distinctions. For practical day-to-day use, each pen stores in the fridge, usually in the door alongside everyday items, and is taken once weekly on the same day each week.

NHS access exists for both, but criteria are strict and waiting lists can be long. Private treatment through a GPhC-registered pharmacy is how many people access these medicines without a referral or a wait. You can read more about where to get weight loss injections legally in the UK if you're working through the access question.

Side effects and what clinical supervision is for

The side-effect profile of both injections is dominated by gastrointestinal symptoms: nausea, loose stools, constipation, indigestion, and burping are the most commonly reported. These tend to be most noticeable in the first days after starting or after each dose increase, and they generally settle. If you are still weighing up your options, it is worth reading through what weight loss injections are available before deciding which route suits you best. Starting slowly on a low dose (one of the design features of both titration schedules) reduces how disruptive this phase is for most people.

Less common but more serious effects include pancreatitis. The MHRA's January 2026 Drug Safety Update on GLP-1 medicines flags acute pancreatitis as an infrequent but potentially serious risk: severe, persistent stomach pain that spreads to the back, with or without vomiting, is the symptom to act on immediately. Gallbladder problems and, in rare cases, allergic reactions are also listed in the patient information for both medicines.

This is precisely why clinical supervision runs throughout treatment, not just at the start. Before you begin, a prescriber reviews your full health picture. At our weight loss treatment page you can see how that process works in practice. If you're ready to take that step, a free consultation with our prescribers is the starting point, no commitment, no fee for the assessment itself.