Two years on Wegovy: where the limit comes from

NICE recommends semaglutide for weight management only if it is used for a maximum of two years and within a specialist weight management service. The figure is quoted constantly and explained almost never, which leaves people assuming it marks the point at which the medicine becomes unsafe or stops working. It does not.

Two things produced it. The specialist weight management services through which the NHS supplies this treatment — tier 3 and tier 4 — are themselves time-limited, and people are usually able to access them for up to around two years. And the economic modelling submitted by the manufacturer, which the appraisal is built on, assumed treatment for a maximum of two years.

So the number describes how long the NHS can realistically deliver the service and what the cost case was built around. It is a commissioning boundary wearing the clothes of a clinical one.

This is the part worth knowing, because it is in the appraisal documents rather than in the headline.

Patient experts told the committee that obesity is a lifelong condition and that continued treatment mattered for holding a result. The committee agreed that treating a chronic condition such as obesity for only two years is not ideal — and then concluded that the two-year assumption was nonetheless reasonable in the context of time-limited NHS services.

Both halves of that are true at once, and the tension is real rather than rhetorical. The limit was a judgement about what could be commissioned, made by a committee that did not think it was clinically ideal.

NICE has opened a review proposal covering this guidance, and the stopping rule is explicitly in scope: stakeholders have asked for both the two-year rule and the specialist-service setting to be re-evaluated.

The reasoning offered is the obvious one, which is that obesity does not resolve after two years. Nothing has changed yet, and a review proposal is not an outcome — but anyone reading the two-year figure as settled should know that the body which set it is looking at it again.

NHS supply. A NICE technology appraisal sets the conditions on which the NHS funds a treatment; it does not describe what is clinically appropriate for someone paying privately.

Private treatment is governed by the medicine's licence and the prescriber's judgement, reviewed at the points set out in our guidance on when treatment is stopped. Tirzepatide, appraised separately, carries no equivalent maximum period at all.

This distinction matters commercially as well as clinically, and it is the reason the two-year figure causes so much confusion: it is quoted as though it were a property of the medicine.

The best data comes from the STEP 1 trial extension. The design matters as much as the result.

STEP 1 randomised 1,961 adults to 68 weeks of weekly semaglutide 2.4 mg or placebo, alongside a lifestyle programme. At week 68 everything stopped, and a subset was followed for a further year off treatment.

At week 68 the trial withdrew the lifestyle intervention as well as the drug. Both arms lost their structured support at the same moment they lost their injection.

That is not a criticism of the trial, which was designed to measure what happens on withdrawal. It is a caution about how the result gets used. "Two-thirds comes back when you stop the medicine" is not quite what was tested; what was tested is what happens when the medicine and the programme around it both end together.

It leaves the more useful question open rather than answered: what happens to someone who stops the drug but keeps the support, the protein intake, the resistance training and the monitoring. The trial was not built to tell us, and anyone citing it as though it were should say so.

The headline figure is regain, and that is the right emphasis — it is why these treatments are understood as managing a chronic condition rather than curing it. But the arithmetic deserves reading properly.

A net 5.6% below baseline at week 120, against 0.1% in the placebo group, is a real difference. Five per cent is also the threshold at which measurable improvements in blood pressure, blood glucose and lipids begin to appear, which is why it is the number the licences use.

So the honest summary is neither "it all comes back" nor "the result holds". Most of it goes, a meaningful part of it stays, and what happens in the year after stopping depends heavily on what replaces the treatment.

Ask what the plan is for after, at the start rather than at the end. A service that treats the end of treatment as the end of its involvement is selling you the easy part.

If you are being treated on the NHS within a specialist service, ask what your local service does at two years — some apply a firm stop, others continue where clinical targets are being met, and the answer varies by area rather than by national rule.

And treat the maintenance phase as its own piece of work rather than as an afterthought. That is the subject our maintenance guidance exists for, and it is the part of this that the two-year argument tends to obscure.