How long should you stay on weight loss injections?

What the trials actually measured, and why that matters for your timeline

The landmark trials that secured UK licences for these medicines were not short experiments. SURMOUNT-1, which studied tirzepatide across thousands of adults with obesity over 72 weeks, showed average body-weight reductions of around 20% at the highest dose. The STEP 1 trial for semaglutide ran for 68 weeks and recorded around 15% average weight loss. Both figures come from the published SURMOUNT-1 paper in the New England Journal of Medicine and its semaglutide equivalent. The point is not just the size of the loss, it's the timescale. Neither trial was measuring a quick fix.

Those numbers reflect participants who stayed on treatment for well over a year. People who stopped earlier in extension studies tended to regain weight steadily over the following months. One widely cited follow-up to STEP 1 found that roughly two-thirds of weight lost during active treatment returned within a year of stopping. That's not a failing of the medicine; it reflects how obesity works as a chronic condition shaped by biology. The idea that you take a course and then you're done is one of the most common misconceptions about these treatments, and it quietly sets people up for disappointment.

None of this means you'll be on injections forever, and if you're wondering how long you can actually be on weight loss injections, the answer depends on your individual progress and clinical circumstances rather than a fixed cut-off. But it does mean that duration should be planned thoughtfully with a prescriber, not cut short because you've hit a target weight or grown impatient with the slower pace that often follows the first few months.

What official UK guidance says about stopping and continuing

NICE has given slightly different guidance depending on which medicine is prescribed. For semaglutide (Wegovy), NICE's technology appraisal TA875 recommends use for a maximum of two years within specialist NHS weight management services, with a review at six months: if you haven't lost at least 5% of your starting weight on the maintenance dose, continuing the treatment may not be recommended. For tirzepatide (Mounjaro), NICE's TA1026 applies the same six-month, 5%-loss checkpoint but does not set a fixed upper time limit in the same way.

These are NHS-commissioning thresholds. Private prescribing follows the licensed indications in each medicine's SmPC, which frame treatment as ongoing alongside lifestyle changes rather than time-limited by default. In practice, a responsible private prescriber will still review duration regularly, looking at how much weight you've lost, whether you've maintained it, whether side effects are manageable, and whether your health goals have shifted.

For most people the realistic picture is this: a period of active dose titration lasting three to six months, followed by maintenance at your highest tolerated dose for as long as treatment remains clinically appropriate and beneficial, and our guidance on how long you should stay on weight loss injections explores that question in more detail. What that means in your case is something only your prescriber can judge.

When stopping sooner might be the right call

Stopping early isn't always the wrong move. If side effects are persistent and seriously affecting your quality of life, if you develop a contraindication, or if a pregnancy is planned, treatment should stop. The medicines are not recommended during pregnancy, while breastfeeding, or when actively trying to conceive, your prescriber will discuss contraception and wash-out timing with you if that's relevant.

There's also the question of what happens when you do stop after a successful period of treatment. Weight maintenance afterwards depends significantly on the lifestyle habits built during treatment, eating patterns, activity levels, sleep. The injections reduce appetite and slow gastric emptying, which creates a window for embedding those habits. Whether that window is enough to sustain weight loss without the medicine varies considerably between individuals, and it's an honest conversation worth having with your prescriber before you stop rather than after. If you're weighing up your options, our page on how long you should take weight loss injections covers the key factors that tend to shape that decision.

If cost is a factor in thinking about duration, our guide to the real cost of weight loss injections lays out what the private market looks like and what you're actually paying for. At nume, every repeat supply is reviewed by a real prescriber (not automatically renewed) so the question of whether to continue is part of every consultation, not an afterthought.

How to approach the conversation with a prescriber

A good starting point is knowing what you want to ask. How long does the prescriber expect it to take to reach a meaningful benefit at your dose? What does the six-month review involve? What would trigger a recommendation to stop? If you transfer to a lower dose or need a break for surgery, how does that affect the plan? Our clinical team at nume reviews every patient's progress before each repeat, so these conversations happen as a matter of course rather than something you have to chase.

You can read more about the full range of UK-licensed weight loss injections and how they compare, or explore your treatment options more broadly. If you still have questions about the process, our frequently asked questions cover many of the practical details. And if you'd like a prescriber to look at your specific situation, the next step is straightforward.