Semaglutide weekly weight loss: what the trial data actually shows

What the STEP 1 trial actually found, and why 'per week' is a tricky figure

The STEP 1 trial, published in the New England Journal of Medicine, followed 1,961 adults with obesity over 68 weeks. Participants on semaglutide 2.4mg lost an average of around 15% of their body weight. Averaged across the full duration, that works out to roughly 0.1–0.2% of body weight per week, but that average masks a more interesting pattern.

Weight loss on semaglutide tends to be fastest in the first few months, then slows as the body adapts and as appetite-reduction effects stabilise. The dose-escalation schedule matters too: at the starting 0.25mg step, the medicine's primary job is tolerability, not maximum effect. Meaningful weight reduction typically accelerates once maintenance doses are reached, and if you want to understand how much semaglutide is used per week across the titration schedule, that page breaks it down clearly. You can read more about how the monthly picture develops on our page covering semaglutide weight loss month by month.

Individual results vary considerably. Age, starting weight, diet, activity, and how well GI side effects are tolerated all play a role. Clinical trial averages tell you what's plausible for a broad population, they don't predict your specific outcome. A prescriber reviewing your full health picture is better placed to set realistic expectations than any headline statistic.

How UK private semaglutide pricing works, and what those headline figures usually leave out

Private semaglutide treatment in the UK is priced per pen per month and varies between providers. Since Eli Lilly's UK list-price adjustment for tirzepatide in September 2025, the market for GLP-1 weight-loss medicines has generally seen prices shift upward across the board, with typical private monthly costs ranging roughly £149–£375 depending on the medicine, dose, and provider, as widely reported. Semaglutide sits within that range depending on where you are in the dose schedule.

What those headline prices often don't include: consultation fees (some providers charge separately for each clinical assessment), prescription fees, delivery charges, and any aftercare or dose-review support between orders. A price that looks lean on comparison sites can expand significantly by the time you reach checkout. For more detail on how Wegovy costs stack up across the private market, our Wegovy price guide sets out the full picture.

It's also worth noting that semaglutide is a prescription-only medicine, any legitimate price will include, or separately charge for, a clinical assessment by a qualified prescriber. If a listing doesn't mention a prescription or a prescriber at all, that's worth pausing on. Our guide on finding legitimate Wegovy supply covers what to look for and what to avoid.

What a single all-inclusive price at a regulated service looks like

At nume, one price covers everything: consultation, prescription, the treatment itself, and priority aftercare seven days a week. There are no hidden fees added at checkout, and nothing billed separately if you need clinical support between orders. We don't run discount codes, voucher promotions, or flash sales, and for a prescription medicine, we think that's the right call. If a seller is promoting GLP-1 weight-loss injections with a promo code or a price that seems implausibly low, the MHRA has been explicit: counterfeit pens are a genuine risk, and fake products have caused hospitalisations.

We're not the cheapest option on the market, and we're not trying to be. What the price buys is a GPhC-registered pharmacy (registration 9012878, verifiable on the GPhC register), photo-ID verification, live weight checks on video, GP notification in line with professional guidance, and a real prescriber reading your case the same day. Your treatment arrives via tracked DPD the next working day, a plain, unmarked box with the pen inside. That's the service.

For a broader look at how semaglutide and tirzepatide compare as treatment options, our weight-loss treatments overview sets out the licensed choices. And if you want to understand the dosing schedule before speaking to a prescriber, the page on how much semaglutide is used for weight loss explains the licensed titration pathway in plain terms.

Why 'cheapest' is the wrong test for a prescription-only medicine

Price comparison makes sense for most things. For a prescription-only GLP-1 medicine sourced through the internet, it's the wrong question. The MHRA's guidance on GLP-1 medicines, available on GOV.UK's drug safety updates, is clear: these are serious medicines that require clinical assessment, a valid prescription, and a supply chain you can trace. A small monthly saving against a provider that skips rigorous ID checks or clinical review isn't a saving, it's a transfer of risk onto you.

The questions that actually matter for a medicine like this: Is the pharmacy GPhC-registered? Does a qualified prescriber review your case, or does software approve it? Is GP notification part of the process? Is there real aftercare if something doesn't feel right? Our about us page sets out how we're built. Our clinical team page for our lead prescriber puts a real name to the oversight.

If weekly weight loss on semaglutide is the number you're most focused on, our page covering how much weight loss per week on Wegovy you might realistically expect gives you the evidence-based range in plain terms. But the more useful question, and one a prescriber can answer for your specific situation, is whether semaglutide is the right medicine, at what pace, and with what support around it. That conversation starts with a free consultation, no commitment, no hidden costs, just a prescriber reading your case the same day.