How fast do you lose weight on Mounjaro – and how much is realistic?

The most important data source is the approval trial SURMOUNT-1 (New England Journal of Medicine, 2022). Around 2,500 adults with obesity, or overweight plus a related condition, but without type 2 diabetes injected tirzepatide or placebo for 72 weeks – in addition to diet and exercise counselling.

The prescribing information (SmPC) gives slightly higher figures for the same trial (16.0 / 21.4 / 22.5 %). The difference comes from the analysis method: the higher figures apply to people who completed the treatment as planned. Depending on the dose, 85 to 91 percent of participants lost at least 5 percent.

Important: these are averages over a year and a half. Which dose is right for you is decided by your doctor – more on this under Mounjaro dosage.

If you break the trial results down, you end up with roughly 0.2 to 0.3 percent of body weight per week on average over 72 weeks. With a starting weight of 100 kg, that would be about 0.2 to 0.3 kg per week or around 1 kg per month – as a long-term average.

In practice, the curve looks different:

• First weeks: Often a noticeable drop, because you eat less, store fewer carbohydrates and lose water in the process. This is not pure fat loss.
• Titration phase: According to the prescribing information, Mounjaro starts at 2.5 mg and is increased in steps. Many people lose weight steadily during this phase, but the full effect only shows on the maintenance dose.
• Later: Weight loss slows down and eventually levels off.

For orientation, here is what the trial averages would mean in kilos (a simple calculation, not a forecast for you):

These figures refer to 72 weeks, i.e. around 17 months – not to the first few weeks. Losing weight faster doesn't automatically mean more success: what matters is that you still eat enough, especially protein, and preserve muscle. More on this under Muscle loss on GLP-1.

An analysis of SURMOUNT-1 (Clinical Obesity, 2025) looked at when weight settles. A plateau was defined as less than 5 percent change over 12 weeks. Depending on the BMI group, the median time to reach it was about 24 to 36 weeks. People on higher doses (10/15 mg), younger people and women tended to reach the plateau later. After that, many still continued to lose weight slowly.

The range in the trials is wide. Some people lose considerably more than average, others considerably less. Typical factors:

• Starting weight: people who weigh more often lose more in kilos – not necessarily in percent.
• Maintenance dose and how well you tolerate it
• Diet, especially enough protein, and exercise
• Sleep, stress, other medications and conditions
• Whether you have type 2 diabetes – in diabetes trials weight loss is usually smaller

You'll find a personal example of the first weeks in Marcus's experience report. Individual journeys are not a forecast for you, though.

A stall on the scale doesn't automatically mean Mounjaro has stopped working. Common reasons are water retention, digestion (especially with constipation), salt, your cycle, new training or simply daily fluctuations of one to two kilos.

Why the number can even go up sometimes is explained in detail under Scale going up despite the weight-loss injection. And if you feel the effect is wearing off over months, read Effect wearing off.

• Don't increase the dose on your own because the scale has stalled
• Don't eat even less to force the pace – it costs muscle
• Don't judge day by day, compare week to week and month to month

The scale alone only tells part of the story. A combination is more meaningful:

• Weight once a week, always the same way: in the morning, on an empty stomach, after using the toilet
• Waist circumference at navel height – it often shows belly fat loss better than the scale
• Strength in training as a rough indicator of muscle preservation
• Side effects, appetite, sleep and energy

Body fat scales (BIA) measure via water content. Because this changes a lot, especially at the beginning, body fat and muscle readings fluctuate considerably. Use them at most as a trend under consistent conditions, not as an exact measurement.

For an overview you can use our free Tracker. Note: this is general information and does not replace medical advice.