Most people researching weight-loss injections start by asking “which one is best?” That is the wrong first question. There is no single best GLP-1 — there is the one that fits your body, your BMI, your comfort with needles and your budget. This GLP-1 decision guide turns that fuzzy choice into five questions you answer in order, finishing with a shortlist of one or two medicines and a sensible price to expect.
The three UK options in play are Mounjaro (tirzepatide), Wegovy (semaglutide) and the newer Wegovy pill (oral semaglutide). A prescriber makes the final call — but knowing where you land before your consultation saves time and stops you overpaying.
Answer five questions — eligibility, weight-loss priority, needles, budget, and support — and each one crosses an option off or moves it up. You will not need all five: most people have a clear shortlist by question three.
Question 1: Are you actually eligible?
This is the gate. Everything else is academic until you clear it. GLP-1 medicines for weight loss are prescription-only, and UK prescribers work to established criteria.
As a general rule, private providers will consider you if your BMI is 30 or above, or 27–29.9 with a weight-related condition such as type 2 diabetes, high blood pressure or sleep apnoea — thresholds that mirror those NICE used for tirzepatide (TA1026). They are a starting point, not a guarantee; the prescriber assesses your full history.
- BMI 30+ — you likely meet the standard weight threshold.
- BMI 27–29.9 with a linked condition — you may qualify on the comorbidity route.
- BMI under 27 — treatment is generally not offered; speak to your GP about other options.
If you are near the lower end, our BMI 27–30 options guide walks through what changes in that band. Clear the gate, and move on.
Question 2: How much weight-loss do you want to prioritise?
The medicines differ in average results, so your target matters. This is where most people first split.
Mounjaro is the only dual-hormone jab — it acts on both GIP and GLP-1 receptors — and it tends to produce the largest average weight loss of the current UK options. In the SURMOUNT-1 trial, tirzepatide averaged around 21% at the highest dose; semaglutide (Wegovy) in STEP 1 averaged around 15%. A head-to-head trial (SURMOUNT-5) put tirzepatide ahead, roughly 20% versus 14%.
Those are trial averages, not promises — your result depends on dose, diet, activity and how your body responds. But the direction is consistent.
Mounjaro moves to the top of your shortlist. If you want the most established, most widely studied option — and Wegovy is the only one shown to cut heart attack and stroke risk in people with existing heart disease (SELECT trial) — Wegovy stays in.
Not sure which of the two fits a first-timer? Our Mounjaro or Wegovy for beginners guide compares them side by side for people who have never injected.
Question 3: How do you feel about needles?
For years this question had no answer — every option was a weekly injection. Now it does. The Wegovy pill is the UK’s first needle-free GLP-1: a daily tablet rather than a weekly jab, with results reported close to the weekly injection.
The trade-off is routine. The pill is taken on an empty stomach with a small sip of water, then you wait around 30 minutes before eating or drinking. The weekly injection is one moment every seven days; the tablet is a small daily discipline.
- Needles are a hard no — the Wegovy pill becomes your lead option.
- Needles are fine, weekly suits you — stay with the injections from question 2.
- Undecided — keep both in; price (next question) often breaks the tie.
Question 4: What is your realistic monthly budget?
Price is where the shortlist usually finalises, because the gap between the cheapest and dearest provider for the same medicine is large. The table below shows the starter dose (the first four-week step) for each medicine, using real figures from our tracked UK providers. Prices last checked 4 July 2026.
| Medicine (starter dose) | Cheapest tracked ongoing price / 4 weeks | Dearest tracked ongoing price / 4 weeks | The Weight Clinic (our pick) |
|---|---|---|---|
| Mounjaro — 2.5 mg | £145.99 | £229 | £160 ongoing (£125 first month with code NEWME) |
| Wegovy — 0.25 mg | £79.97 | £164 | £115 ongoing (£80 first month with code NEWME) |
| Wegovy pill — 1.5 mg | £99 | £115 | £115 ongoing (£80 first month with code NEWME) |
Two things stand out. The starter dose is the cheap step — a low, four-week introductory dose, not the treatment dose — so costs rise as you titrate upward; budget for the maintenance dose, not the headline first month. And the same medicine varies by roughly £80–£85 across providers, so where you buy matters as much as what you buy. You can see every tracked provider ranked by price on our home comparison table — always sorted cheapest-first, with no pay-to-move-up.
For most readers who finish this guide, our recommended provider is The Weight Clinic — a GPhC-registered pharmacy carrying all three medicines, with monthly video reviews and a refund if you are declined, so you are not out of pocket for a “no”. New customers get £35 off the first order with code NEWME.
Question 5: How much support and structure do you want?
The medicine is only part of it. Some people want the pen posted and nothing else; others do better with check-ins, coaching and a prescriber who reviews progress. This question does not change which medicine you pick — it changes which provider you pick it from.
Look at three things in a provider’s listing: whether reviews are monthly or one-off, whether there is a subscription lock-in, and what happens if you are declined. A refund-if-declined policy means you are not charged for an assessment that ends in “not suitable”, and monthly video reviews mean a prescriber actually watches your titration rather than auto-shipping the next pen.
Only ever buy from a UK-regulated pharmacy or clinic (GPhC and, where relevant, CQC). Steer clear of anywhere selling “compounded” or unbranded tirzepatide/semaglutide — those are not the same as the licensed medicines and sit outside UK regulation.
Putting the five answers together
Read your five answers back as a sentence: “I clear the BMI gate, I want strong results, I’m fine with a weekly needle, my budget is around £160–£200 a month at maintenance, and I want monthly reviews.” That sentence points cleanly at Mounjaro from a review-led provider. Change one answer — needles are a no — and it points at the Wegovy pill instead.
That is the whole method: five questions, each narrowing the field until the choice makes itself. Want the same logic as a single flowchart? Our which GLP-1 is right for me guide maps it visually. Already on a medicine and weighing a change? See switching between GLP-1 medications.
Frequently asked questions
Do I have to answer all five questions in order?
Order matters for the first four. Eligibility is the gate — there is no point comparing medicines you cannot be prescribed. After that, weight-loss priority, needle preference and budget each remove or reorder options. Question five is about the provider, not the medicine, so it comes last. Most people have a clear shortlist before they even reach it.
Is Mounjaro always the right answer if I want to lose the most weight?
On trial averages, tirzepatide (Mounjaro) tends to produce more weight loss than semaglutide (Wegovy) — roughly 20% versus 14% in the SURMOUNT-5 head-to-head. But averages are not individuals, and a prescriber may recommend Wegovy for reasons specific to you, such as its proven cardiovascular benefit in people with existing heart disease. The five-question method gives you a shortlist; the prescriber confirms it.
The starter-dose price looks affordable. Will it stay that low?
No — the starter dose is a low four-week introductory step, not a treatment dose. As you titrate upward, the price per four weeks rises. When you budget, use the maintenance-dose price for your likely target dose, not the first-month promotional figure. Our home table shows every dose step so you can plan ahead.
Why does the same medicine cost so differently between providers?
Providers set their own margins, promotions and support packages. For the Mounjaro starter dose our tracked ongoing prices run from about £145.99 to £229 for the identical medicine. That is why our table always ranks by price and why comparing providers — not just medicines — is worth a few minutes.
What if the five questions leave two options tied?
A tie usually means budget and support break it. If two medicines both fit and you are undecided, pick the provider with monthly reviews and a refund-if-declined policy, and let the prescriber weigh in during the consultation. You lose nothing by being assessed for the one you lean towards.
The Weight Clinic is our recommended provider — a GPhC-registered pharmacy carrying Mounjaro, Wegovy and the Wegovy pill, with monthly video reviews and a refund if you are declined. New customers save £35 on the first order with code NEWME. Confirm the current price and check your eligibility on their site.