Weight loss injections: what to decide before your first dose

Which injection is actually available to you — and through which route?

This is the decision most people haven't fully thought through. Both Mounjaro and Wegovy are licensed in the UK for weight management, but NHS access is tightly phased. As of summer 2026, NHS tirzepatide is available to people with a BMI of at least 40 and four or more qualifying conditions; the current NHS Wegovy pathway sits inside specialist weight management services with commonly long waiting times. Most people asking about weight loss injections in the UK right now won't meet the current NHS criteria or can't wait.

Private treatment through a regulated pharmacy is the alternative, and it's the route to understand carefully. The legal requirement is the same either way: a prescriber assesses your health, confirms the medicine is appropriate, and issues a prescription. What varies is the process and the time it takes. At nume, a GPhC-registered Independent Prescriber reads your consultation personally, the same day, a real clinician, not software. If approved, treatment is dispatched that afternoon for next-working-day delivery. That's a practical difference worth knowing about if you're trying to fit this into a working week.

The NHS England guidance on weight management injections sets out both pathways clearly, including the wraparound diet and activity support that accompanies NHS prescribing.

Which injection suits your medical picture?

Mounjaro activates two receptors (GIP and GLP-1) making it the only dual-agonist weight-loss medicine licensed in the UK. Wegovy works on the GLP-1 pathway alone. In the SURMOUNT-1 trial published in the New England Journal of Medicine, tirzepatide produced around 20–21% average body-weight reduction at 15mg over 72 weeks. STEP 1 found semaglutide 2.4mg produced roughly 15% average reduction over 68 weeks. The SURMOUNT-5 head-to-head trial confirmed tirzepatide produced greater average loss, though both medicines show meaningful results for most participants.

The right one for you depends on your full health picture. Type 2 diabetes, existing cardiovascular risk, other medicines you take, all of these feed into a prescriber's thinking. You can read about the individual medicine options in more detail, but the clinical assessment is where the real matching happens. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance, so it's worth checking even if you're not sure you qualify.

Injection site and frequency are identical for both: once weekly, into the abdomen, thigh or upper arm, rotating the spot each time. If the injection itself is the thing making you hesitate, our guide on how to do the injection walks through it step by step.

What does ongoing treatment actually involve?

Both medicines start at a low dose (2.5mg for tirzepatide, 0.25mg for semaglutide) not because those doses drive the weight loss directly, but because starting gently gives your digestive system time to adjust. The dose increases roughly every four weeks under prescriber guidance, working towards the maintenance dose that's right for you. Frequency is fixed: once a week, same day each week where possible.

The pens are pre-filled and kept in the fridge. If you order before 12pm on a weekday, your pen arrives with DPD the next working day, practical if you're juggling a job and need to plan ahead. Storage once it's with you means keeping it refrigerated; the exact room-temperature window is in the patient information leaflet and should be followed to the letter, because pen integrity matters.

There's also the question of what happens between doses. Aftercare (somewhere to flag a concern on a Sunday, a prescriber to ask about a change in how you're feeling) is not optional extra. The common questions people ask mid-treatment tend to centre on side effects and timing. Understanding the side-effect profile before you start is genuinely useful: nausea, burping, constipation and reflux are common, generally mild and tend to ease off. Seek urgent medical help for severe, persistent stomach pain spreading to your back, this can be a sign of pancreatitis, which the MHRA flagged in a Drug Safety Update in January 2026 as an infrequent but serious side effect of GLP-1 medicines.

Cost: what you're actually comparing

If you've searched for cheaper options, you'll have found prices ranging from around £149 to over £375 per month depending on dose and provider. Eli Lilly raised Mounjaro's UK list price from 1 September 2025, and private prices have moved with it. The comparison that matters isn't the headline monthly figure, it's what that price includes. Consultation fees, prescription charges, delivery costs and ongoing aftercare are sometimes bundled, sometimes not.

At nume, one transparent price covers the consultation, the prescription, next-working-day tracked delivery and seven-day aftercare, no subscription, no hidden add-ons, and no auto-renewal. Current treatment pricing is on the treatment page. What we don't do is compete on being the cheapest: for a prescription medicine dispensed from a GPhC-registered pharmacy, clinical rigour is a more useful measure than the lowest number you can find.

Worth checking: any legitimate source of these medicines will require a prescription following a clinical assessment. Pens offered without one are a serious red flag, the MHRA has warned repeatedly about counterfeit weight loss pens sold online, some containing insulin. If you're based in Northern Ireland and exploring your options locally, you can find out more about weight loss injections available in Newry. You can verify any online pharmacy on the GPhC register; our premises registration number is 9012878.

If you've thought through the options and want to take the next step, start your free consultation and a prescriber will review your application the same day.