Has Mounjaro stopped working, or have you reached a plateau?

First, which question are you asking?

Mounjaro stopped working. You lost weight steadily and then it stalled, or started creeping back up. That is this article.

You never really got going. Weight has barely moved since you started. That is a different question — about dose, about what else is being treated, and about what has not been looked for — and never really responded to Mounjaro is covered separately. For the broader question of limited response to semaglutide and what “GLP-1 resistance” means, see the clinical overview.

A plateau is not a failure

It feels like one. It usually is not.

A smaller body needs less energy to run. Every kilogram lost lowers what you burn at rest, during movement and digesting food. So a dose that produced steady loss at your starting weight produces less at your current one, through no fault of the treatment and none of yours.

That is why almost everyone plateaus eventually, and why the plateau arriving says very little about whether treatment is working. What it tells you is that the balance has moved and something needs to change if you want the loss to continue — or that you have reached a weight your body is holding, which may be a perfectly reasonable place to be.

What you lost along the way

Weight loss of any kind takes some muscle with it. Muscle is metabolically expensive tissue, so losing it lowers what you burn at rest further still.

The more muscle lost on the way down, the lower the plateau sits and the easier regain becomes. This is why protein intake and resistance exercise are not optional extras alongside treatment, and why body composition — what the weight is actually made of — tells you more at this point than the number on the scales does.

Two people at the same weight, one who protected muscle and one who did not, are in materially different positions.

Have you reached the ceiling?

The highest dose studied for weight management in the SURMOUNT-1 trial was 15 mg. If you are already there, further loss has to come from somewhere other than the prescription.

If you are not, there may be room — but a dose increase is a clinical decision made on tolerability and the whole picture, not an automatic next step because the scales stopped moving.

What happens if you stop

This is the part worth knowing before deciding the treatment has failed and abandoning it.

The SURMOUNT-4 trial took people who had lost at least 10% of their body weight over 36 weeks on tirzepatide, then either continued them on treatment or switched them to placebo. A year after withdrawal, 82% of those taken off treatment had regained more than a quarter of what they had lost. A quarter of them had regained three quarters or more.

The improvements beyond weight followed the same pattern. Waist circumference, blood pressure, cholesterol, HbA1c and fasting insulin all moved back in proportion to how much weight returned. The metabolic benefit went with the weight.

A plateau at a lower weight, held, is a better outcome than a plateau abandoned.

Is this a plateau, or is it your weight now?

The honest question, and the one that rarely gets asked.

Not everyone should keep losing. For some people the weight they have reached is where the health benefit has largely been realised and the sensible plan is to hold it — which is itself active treatment, not stopping. For others the plateau has arrived early, with meaningful risk still present, and it needs working through.

Those are different conversations and they depend on what else is going on: what the blood results show now compared with before, what the body composition looks like, whether sleep apnoea, thyroid or insulin resistance are still in play, and what your original reason for treatment was.

What a review should cover

Not just whether to increase the dose.

Where you started and where you are, measured properly rather than by weight alone. Repeat bloods, so the metabolic picture now can be compared with the one at the beginning. Body composition. What has changed in your life, your sleep and your other medicines since you started. And a straight answer about whether the aim from here is further loss or holding what you have.

If the only thing being reviewed is the prescription, that is not a review of your treatment.