How long should you take tirzepatide — and what does the evidence say?

The 72-week trials: why that number keeps appearing

The SURMOUNT-1 trial (the large phase 3 study whose results were published in the New England Journal of Medicine) ran for 72 weeks and showed average body-weight reductions of around 20–21% at the highest dose. That 72-week figure is not arbitrary: it reflects how long it took participants to approach a weight plateau. Most of the loss happened in the first 36 weeks, but the body continued to respond for many months after that.

What happened when the medicine stopped is equally instructive. SURMOUNT-4, the follow-on withdrawal study, found that participants who switched to placebo after 36 weeks of tirzepatide regained a substantial portion of their lost weight within a further year. The biology is straightforward: tirzepatide works while you take it. The appetite and metabolic signals it modulates return towards their previous baseline once the medicine clears.

That does not mean lifelong treatment is obligatory for everyone. Some people reach a stable, lower weight with improved health markers and choose, in discussion with their prescriber, to reduce or stop. Others find that the medicine is managing an ongoing biological tendency and treat it accordingly. Neither path is wrong. If you are weighing up your options, our page on how long you should take Mounjaro walks through the key considerations to help inform that clinical conversation.

The six-month review: NICE's built-in checkpoint

NICE recommends tirzepatide for weight management in adults meeting specific BMI criteria, and the appraisal (TA1026, published December 2024) includes a practical checkpoint: if someone has not lost at least 5% of their starting body weight after six months at the highest dose they tolerate, the prescriber should review whether continuing is justified.

This is worth understanding clearly. The six-month review is not a countdown to stopping. It is a safety net to catch people for whom the medicine is not working, so they are not exposed to an ineffective treatment indefinitely. For the majority of people who do respond, it is simply a scheduled check-in that confirms treatment is worthwhile and should continue.

A quick habit worth building: weigh yourself at the same time of day (first thing in the morning, before eating) and note it once a week. A simple note in your phone over several months gives you and your prescriber something concrete to discuss at each review, without the noise of day-to-day fluctuation.

If you are curious about how the cost of ongoing treatment fits your budget, our Mounjaro pricing page explains what the private prescription price covers at each stage.

Is there a maximum, and how does this differ from Wegovy?

There is currently no NICE-mandated maximum duration for tirzepatide used privately. The picture is different for semaglutide (Wegovy): NICE's appraisal for that medicine sets a two-year ceiling for NHS-funded treatment within a specialist weight-management service. Tirzepatide carries no equivalent ceiling in its own NICE appraisal, though it does carry the Black Triangle designation, meaning it is still subject to additional post-market surveillance by the MHRA.

In practice, continuation is reviewed before every repeat prescription. At nume, a GPhC-registered Independent Prescriber reads each follow-up, checks your progress and flags anything that warrants a closer look. There are no automatic renewals. If circumstances change (pregnancy, a new diagnosis, intolerable side effects) treatment is paused or stopped at that point, not at a pre-set date.

For a broader picture of what the medicine is and how it works in the body, the Mounjaro overview covers the mechanism in plain terms. Questions about how quickly results typically appear are covered on our how long Mounjaro takes to work page.

Practical implications for people taking tirzepatide privately

Most adults who respond well to tirzepatide find they are taking it for at least 12 to 18 months before they and their prescriber have a full picture of where their weight settles. Some continue beyond that. The NHS tirzepatide page notes that this is a treatment to be taken alongside a reduced-calorie diet and increased physical activity (not instead of them) and that the lifestyle component matters for long-term outcomes whether or not the medicine continues.

Related questions about the timeframe of treatment come up often. Our pages on how long to stay on tirzepatide and how long tirzepatide can be taken safely go into further detail. If you would like to explore whether treatment is right for you, check your eligibility through a free consultation with our prescribing team.