Why some people don't lose weight on Wegovy — and what to do about it

The trial numbers are averages, and you are not an average

The STEP 1 trial, published in the New England Journal of Medicine, enrolled adults with obesity or overweight and found an average weight reduction of approximately 15% over 68 weeks at the 2.4mg maintenance dose. That figure is widely quoted. What gets less attention is the spread underneath it: some participants lost more than 20% of their body weight, while others, following exactly the same protocol, lost very little. Non-response is documented, not exceptional.

Why the gap? Semaglutide works by activating GLP-1 receptors involved in appetite signalling and gastric emptying. How powerfully those receptors respond varies between people, influenced by genetics, baseline insulin sensitivity, gut microbiome composition and other factors researchers are still characterising. None of this is a character failing. It is biology, and it is the reason the same pen produces different outcomes in different bodies.

There is also the question of tolerability. People who experience significant nausea early on sometimes stay at lower doses longer than the standard schedule, which reduces exposure at the therapeutic maintenance level. If nausea keeps someone from reaching 2.4mg, the results at 1.0mg or 1.7mg will naturally be more modest. That is a medical management question, not evidence that the medicine cannot work for them.

The 5% threshold, and what NICE says happens next

NICE's recommendation for semaglutide (TA875) includes a clear checkpoint: if weight loss is below 5% after six months at the maintenance dose, continuation should be reconsidered. That threshold exists for a practical reason. Below 5%, the balance of ongoing side-effect burden against clinical benefit is harder to justify, and resources (NHS or private) are better directed elsewhere.

Reaching that point is not a dead end, though. It is a clinical decision point. A prescriber looking at a six-month plateau will ask: has the person actually been on maintenance dose for that whole period, or were they dose-escalating for most of it? Has injection technique been consistent? Is there a medicine interaction affecting absorption? Sometimes the answer is to stay the course a little longer; sometimes it is to switch.

For people whose results with semaglutide are disappointing, tirzepatide (Mounjaro) is a different option. It activates both GLP-1 and GIP receptors, and in the SURMOUNT-5 head-to-head trial produced greater average weight loss than semaglutide 2.4mg. Some people who respond modestly to one GLP-1 mechanism respond more strongly to the dual approach. You can read more about how semaglutide works and what Wegovy involves before a consultation.

Adherence, routine and the practical things that matter

Adherence sounds like a euphemism for blaming the patient. It is not meant that way here. Semaglutide has a half-life that accommodates a missed week without catastrophe, but repeated missed doses (especially during the dose-escalation phase) blunt the medicine's effect meaningfully. A question our prescribers hear fairly often is whether an occasional gap explains a slow start. Sometimes it does.

Routine helps more than people expect. Some patients find that attaching the injection to a fixed moment (the same evening the pen comes out of the fridge door, before dinner on a Sunday) reduces missed doses to near zero. That kind of anchor is small, but consistency across 68 weeks compounds. When weight loss typically begins on Wegovy is a related question worth reading if you are in the early weeks and wondering whether progress is on track.

Diet and activity remain relevant too. Wegovy reduces appetite substantially in most people, but it is licensed alongside a reduced-calorie diet and increased physical activity, not instead of them. Someone eating well past satiety signals, or whose diet is very high in processed foods that bypass the fullness cues GLP-1 generates, may see blunted results. This is not a moral judgement; it is a physiological one.

What to do if you are not responding, a practical decision frame

If weight loss has stalled or never really started on Wegovy, the conversation belongs with a prescriber, not a forum. The right questions are: which dose have you actually reached, and for how long; what does the pattern of any weight change look like week to week; are there medical factors such as thyroid function or other medicines that might be in play?

Some people reading this page are weighing up whether to start Wegovy knowing non-response is possible, and that is a reasonable thing to factor in. Others are already on treatment and frustrated. Both situations are worth discussing openly with a clinician rather than stopping quietly or persevering past the point where the evidence supports it. You can explore what typically happens after stopping Wegovy if that is part of your thinking, or look at the broader picture of weight-loss treatment options to understand what else is licensed.

On the cost side, it is worth knowing that private Wegovy pricing varies by provider and dose, a realistic breakdown of what Wegovy costs privately in the UK can help you plan if you are considering longer-term treatment. And if you want to understand the full results picture rather than just the non-response end, how weight loss on Wegovy typically unfolds covers the evidence in more detail.

At nume, a real prescriber reviews your consultation the same day (not software) and that includes looking at whether a medicine is likely to be a good fit for you before any prescription is issued. If you want a clinical view on your situation, speak to our prescribers through a free consultation.