What does a Mounjaro weight loss graph actually show?

What does the weight loss curve look like across 72 weeks?

The SURMOUNT-1 trial enrolled 2,539 adults with obesity and tracked their weight weekly. The resulting tirzepatide weight loss graph has a recognisable shape: a sharp initial descent in the first 12–16 weeks, a still-declining but gentler slope through the middle of the trial, and a gradual approach toward a plateau in the final stretch. That plateau is not fully reached by week 72 at the 15mg dose, suggesting the medicine's effect had not yet exhausted itself when the trial closed.

Participants on placebo lost a little weight too, probably reflecting the lifestyle support all groups received. What separates the tirzepatide lines is how far below placebo they fall and how consistently they stay there. The 15mg line reached an average reduction of around 20–21% of starting body weight. At 10mg the figure was around 19.5%; at 5mg around 16%. The gap between doses is visible on the graph but the lines follow broadly parallel paths, each one a shifted version of the same curve.

This data is published in the SURMOUNT-1 paper in the New England Journal of Medicine and formed the basis for NICE's recommendation of tirzepatide in TA1026.

Why is the loss fastest at the start, and does it slow down later?

The steep early gradient is partly a biological response to appetite suppression kicking in fully, and partly a reflection of dose escalation. Mounjaro, the weight loss jab that has drawn considerable attention since its UK launch, starts at 2.5mg, a dose chosen to help the body adjust rather than to produce the maximum effect immediately. As the prescriber moves through the titration schedule, the dose increases and so does the appetite-reducing signal. Each step up contributes another increment of loss that compounds through the graph's early weeks.

By around week 20–28, most participants are on or approaching their target maintenance dose. Weight loss continues, but the body is also adapting its energy expenditure in response to lower calorie intake, which is a normal physiological response and is why the curve flattens rather than continuing at the initial gradient. This does not mean the medicine has stopped working. A useful habit: weigh yourself on the same day each week, at the same time, and track the monthly average rather than the daily number, weekly fluctuations from water retention and digestion can make a still-falling graph look like a plateau when it isn't.

Understanding how the titration schedule shapes results is covered in more depth on our Mounjaro weight loss overview.

Does the graph tell us what happens when treatment stops?

This is where the clinical picture becomes more complex, and the graph is honest about it. Extension and withdrawal data from the tirzepatide programme show that when treatment stops, body weight tends to increase. The curve reverses. This is not a peculiarity of Mounjaro; it reflects the underlying biology of obesity as a long-term condition rather than a one-time intervention.

NICE's appraisal of tirzepatide (TA1026) discusses the evidence base and includes commentary on sustained use. The NHS England guidance on weight management medicines similarly frames these treatments as long-term tools within a broader programme that includes diet and activity changes, rather than short courses.

For people considering private treatment, the cost picture over time matters as much as the early results. Graphs are a compelling starting point; your prescriber's job is to translate what they show into a plan that fits your actual health profile. Our clinical team is available 7 days a week for aftercare, questions about your own progress or what the numbers mean for you are exactly what they are there for.

How does this compare with other weight loss injection data?

The head-to-head SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025, plotted tirzepatide and semaglutide 2.4mg on the same graph across 72 weeks. The tirzepatide line sat lower (meaning greater average weight reduction) throughout most of the trial period. The gap widened in the middle weeks before narrowing slightly toward the end. The total Mounjaro weight reduction seen across trials brings the higher tirzepatide doses close to the approved 7.2mg semaglutide dose (Wegovy), whose own trial data suggests average loss of around 20.7% at 72 weeks.

If you are weighing up which option fits your circumstances, our weight loss treatment overview sets out the licensed options side by side, and the clinical team at our prescriber team page gives a sense of who reviews your case. For a broader grounding in what tirzepatide is and how it works mechanically, the tirzepatide overview is a good next step. The eight-week results page covers the early part of the curve specifically, which is often what people are most curious about when they are just getting started.