How much weight can you lose on Mounjaro or Wegovy, and how fast? What the clinical trials show, a realistic month-by-month timeline, and what affects your results.
How much weight can you lose on Mounjaro or Wegovy?
In the main clinical trials, people taking Wegovy lost an average of around 15% of their body weight over 68 weeks, and people taking the highest dose of Mounjaro lost an average of around 21% over 72 weeks.
That is significantly more than most people achieve through diet and exercise alone.
But these figures come with important context:
- They are averages. Some people lost much more, and some lost much less.
- They were achieved over more than a year, not a few weeks.
- Participants were also following a reduced-calorie diet and increased physical activity.
- Weight loss is usually faster in the early months and slows down over time.
This guide explains what the research shows, what a realistic timeline looks like month by month, what affects your results, and how to tell whether treatment is working for you.
What the clinical trials show
Wegovy: the STEP 1 trial
The STEP 1 trial studied semaglutide 2.4 mg (the maintenance dose of Wegovy) in adults with obesity, or overweight with at least one weight-related condition, who did not have diabetes.
After 68 weeks:
- People taking semaglutide lost an average of 14.9% of their body weight
- People taking a placebo lost an average of 2.4%
- Around one in three people taking semaglutide lost 20% or more of their body weight
Mounjaro: the SURMOUNT-1 trial
The SURMOUNT-1 trial studied tirzepatide (Mounjaro) at three maintenance doses in a similar group of adults.
After 72 weeks, average weight loss was:
- 15.0% on the 5 mg dose
- 19.5% on the 10 mg dose
- 20.9% on the 15 mg dose
- 3.1% on placebo
More than half of the people taking the 15 mg dose lost 20% or more of their body weight.
What does this mean in kilograms?
Percentages can be hard to picture, so here is an illustration:
- A person starting at 100 kg who loses 15% would lose about 15 kg
- A person starting at 100 kg who loses 21% would lose about 21 kg
- A person starting at 120 kg who loses 15% would lose about 18 kg
These are illustrations based on trial averages, not predictions of what any individual will lose.
A realistic timeline: what to expect month by month
Everyone responds differently, but most people follow a broadly similar pattern.
A key point to understand first is that both Mounjaro and Wegovy start at a low dose that is gradually increased. This is known as dose escalation, and it helps your body adjust and reduces side effects.
That means you are not taking the full therapeutic dose during the first few months.
The typical dose schedules
Mounjaro usually starts at 2.5 mg once weekly for four weeks. The dose is then increased in 2.5 mg steps, at least four weeks apart, as needed and as tolerated. Maintenance doses are 5 mg, 10 mg or 15 mg. The 2.5 mg dose is a starting dose, not a maintenance dose.
Wegovy usually starts at 0.25 mg once weekly, increasing every four weeks through 0.5 mg, 1 mg and 1.7 mg, before reaching the 2.4 mg maintenance dose from around week 17.
Your prescriber may adjust this schedule depending on how you respond and any side effects.
Weeks 1 to 4: getting started
In the first month, many people notice:
- Reduced appetite and feeling full sooner
- Fewer cravings and less "food noise"
- Some side effects, such as nausea, constipation or indigestion
Some people see a noticeable drop on the scales in the first few weeks. Part of this early change can be fluid and reduced stomach contents rather than fat alone.
Other people see only a small change in the first month. This is normal, particularly on the starting dose.
Months 2 to 3: building momentum
As the dose increases, appetite suppression often becomes stronger and weight loss more consistent.
By this stage, many people are settling into new eating habits, such as smaller portions and fewer snacks.
Side effects may flare for a few days after each dose increase and then settle.
Months 4 to 6: reaching your maintenance dose
Many people reach their effective maintenance dose during this period.
For many, this is when weight loss is most steady. By around six months, many people have lost a meaningful percentage of their starting weight.
The six-month point is also an important milestone for reviewing whether treatment is working. NICE guidance for Mounjaro, for example, recommends considering stopping treatment if a person has lost less than 5% of their starting weight after six months on the highest tolerated dose.
Months 6 to 12: slower, steady progress
Weight loss usually continues but at a slower rate than in the first few months.
This is expected. As you lose weight, your body needs less energy, and your body adapts to the lower intake.
In the trials, most of the weight loss happened in roughly the first year.
Beyond 12 months: the plateau and maintenance phase
In both STEP 1 and SURMOUNT-1, weight loss gradually levelled off during the second half of the trials.
Reaching a plateau does not mean the medicine has stopped working. It usually means your body has reached a new balance point while on treatment.
At this stage, the focus often shifts from losing weight to maintaining your new weight and building habits for the long term.
Why weight loss is not a straight line
It is very common for weight to go down, stay the same for a week or two, and then drop again.
Short-term fluctuations can be caused by:
- Changes in fluid balance
- Salt and carbohydrate intake
- Constipation
- The menstrual cycle
- Hormonal changes
- Timing of weighing
- Exercise, particularly new strength training
Look at the trend over several weeks rather than day-to-day changes.
Weighing yourself once a week, at the same time of day, in similar clothing, gives a more reliable picture.
What affects how much weight you lose?
Results vary widely between individuals. Factors that can influence your results include:
Your dose
In SURMOUNT-1, higher maintenance doses of Mounjaro were associated with greater average weight loss. However, the right dose is the one that works for you with manageable side effects. More is not automatically better.
Consistency
Missing doses, taking breaks or delaying dose increases can slow progress.
Diet quality
Weight loss injections reduce appetite, but what you eat still matters. Our guide on what to eat on Mounjaro or Wegovy explains how to get the most from your treatment.
Alcohol
Alcohol adds calories and can undermine food choices. Read our guide on drinking alcohol on Mounjaro or Wegovy.
Physical activity
Activity supports weight loss and, importantly, strength training helps protect muscle during weight loss. Read more in our article on weight loss injections and muscle loss.
Type 2 diabetes
People with type 2 diabetes often lose somewhat less weight on average than people without diabetes in clinical trials, although the health benefits can still be substantial.
Other medicines and health conditions
Some medicines, such as certain antidepressants, antipsychotics, steroids and insulin, can make weight loss more difficult. Conditions such as an underactive thyroid can also affect progress.
Sleep and stress
Poor sleep and high stress levels can affect appetite, cravings and energy levels.
Starting weight
People with a higher starting weight may lose more kilograms, even if the percentage lost is similar.
Is Mounjaro more effective than Wegovy?
On average, the evidence suggests that Mounjaro tends to produce greater weight loss than Wegovy.
In the SURMOUNT-5 trial, which compared the two medicines directly, people taking tirzepatide lost an average of 20.2% of their body weight after 72 weeks, compared with 13.7% for semaglutide.
However, averages do not tell you how an individual will respond. Some people do very well on Wegovy and some people tolerate one medicine better than the other.
Wegovy also has evidence showing a reduction in the risk of major cardiovascular events, such as heart attack and stroke, in people with established cardiovascular disease and overweight or obesity.
The right choice depends on your health, goals and preferences. You can read a full comparison in our article: Is Mounjaro better than Wegovy?
How fast is too fast?
Rapid weight loss can feel exciting, but faster is not always better.
Very rapid weight loss can increase the risk of:
- Loss of muscle
- Gallstones
- Dehydration
- Nutritional deficiencies
- Fatigue and weakness
- Hair shedding
If you are losing weight very quickly while struggling to eat or drink, feeling weak or dizzy, or experiencing persistent vomiting, speak to your prescriber. Your dose or treatment plan may need reviewing.
Never increase your dose faster than prescribed in an attempt to speed up weight loss.
What if you are not losing weight?
If your weight loss is slower than expected, try not to become discouraged too early.
It is common for progress to be slow on the starting doses, and some people take longer to respond.
If you have been taking a maintenance dose for several months and are not losing weight, there may be a reason. Our article on why you may not be losing weight on Mounjaro or Wegovy explains the seven most common causes.
Your prescriber can also review your dose, your diet and activity, and whether another treatment may be more suitable.
Look beyond the scales
Your weight is one measure of progress, but not the only one.
Many people notice improvements well before they reach their goal weight, including:
- Clothes fitting more loosely
- A smaller waist measurement
- More energy
- Better sleep
- Less joint pain
- Improved mobility and fitness
- Improved blood pressure, blood sugar or cholesterol
- A healthier relationship with food
- Greater confidence
Even 5% to 10% weight loss can bring meaningful health benefits, such as improvements in blood pressure, blood sugar and cholesterol, and a reduced risk of type 2 diabetes.
Tracking your waist measurement, taking progress photos and noting how you feel can give a more complete picture than the scales alone.
For some people, losing weight also improves other areas of health. For example, our article on whether losing weight improves erectile dysfunction explores the link between weight and sexual health in men.
How to get the best results from Mounjaro or Wegovy
Practical steps that can support your results include:
- Take your injection on the same day each week
- Follow your dose schedule and do not skip dose reviews
- Eat protein at every meal
- Build up fibre from vegetables, fruit, pulses and wholegrains
- Drink enough fluids
- Limit alcohol
- Do strength training at least twice a week if you can
- Walk more and build daily activity
- Prioritise sleep
- Weigh yourself weekly, not daily
- Report side effects to your prescriber rather than stopping treatment without advice
What happens when you reach your goal?
When you reach a healthy weight or your personal goal, the next question is what happens next.
Research shows that many people regain a significant proportion of their weight after stopping weight loss injections, particularly if lifestyle changes are not maintained.
Options may include continuing treatment, reducing the dose, or stopping with a plan in place. This should always be discussed with your prescriber.
Read more in our article on what happens when you stop Mounjaro or Wegovy.
Real results from SynovaMed patients
Every patient's journey is different. To see what treatment can look like in practice, read Nicola's success story.
If you would like to find out whether Mounjaro or Wegovy may be suitable for you, you can start an online consultation through our weight loss programme. You can also meet our clinical team.
Frequently Asked Questions
How much weight can you lose on Mounjaro?
In the SURMOUNT-1 trial, average weight loss after 72 weeks was 15.0% on 5 mg, 19.5% on 10 mg and 20.9% on 15 mg. Individual results vary.
How much weight can you lose on Wegovy?
In the STEP 1 trial, people taking semaglutide 2.4 mg lost an average of 14.9% of their body weight after 68 weeks. Individual results vary.
How much weight can you lose on Mounjaro in the first month?
It varies. Some people notice a clear drop in the first month, while others see only a small change on the 2.5 mg starting dose. Early weight loss often includes some fluid.
How long does it take for Mounjaro to start working?
Many people notice reduced appetite within the first few weeks. Weight loss usually becomes more consistent as the dose increases over the following months.
How long does it take for Wegovy to start working?
Appetite changes are often noticed within the first few weeks, but the full maintenance dose is usually reached from around week 17, and weight loss often becomes more consistent over time.
How much weight can you lose on Mounjaro in 3 months?
Results vary widely. Most people are still increasing their dose at three months, and progress depends on dose, diet, activity and individual response.
Why has my weight loss slowed down on Mounjaro?
Weight loss naturally slows as your body adapts and needs less energy. Plateaus are common, particularly after the first few months. Speak to your prescriber if you are concerned.
Is Mounjaro better than Wegovy for weight loss?
On average, Mounjaro produced greater weight loss than Wegovy in the head-to-head SURMOUNT-5 trial. However, individual responses vary and the right medicine depends on your circumstances.
What happens if I do not lose weight on Mounjaro?
If you have lost less than 5% of your starting weight after six months on the highest tolerated dose, your prescriber may review whether treatment should continue.
Is it safe to lose weight quickly on Mounjaro or Wegovy?
Weight loss should be monitored. Very rapid weight loss can increase the risk of muscle loss, gallstones and dehydration. Speak to your prescriber if you are losing weight very quickly or feel unwell.
Do you keep losing weight on Mounjaro forever?
No. Weight loss usually slows and levels off after roughly a year. At this point, the focus shifts to maintaining your results.
The bottom line: how much weight can you lose on Mounjaro or Wegovy?
Clinical trials show average weight loss of around 15% with Wegovy and up to around 21% with the highest dose of Mounjaro, over roughly 16 to 18 months.
But your own results will depend on many factors, and the journey is rarely a straight line.
The most realistic expectations are:
Slower progress on the starting doses.
Steadier weight loss once you reach your maintenance dose.
Natural fluctuations from week to week.
A gradual slowing and plateau after around a year.
Better results when treatment is combined with a healthy diet, strength training and good habits.
Focus on steady, sustainable progress rather than the fastest possible drop on the scales, and remember that improvements in your health, energy and wellbeing matter just as much as the number itself.
Medical Disclaimer
This article is intended for general educational purposes and does not replace personalised medical advice, diagnosis or treatment. The weight loss figures quoted are averages from clinical trials and do not predict individual results. Mounjaro, Wegovy and other prescription weight-management medicines are not suitable for everyone. Always follow the dosing and treatment advice provided by your healthcare professional. If you experience significant weakness, persistent vomiting or diarrhoea, severe abdominal pain or other concerning symptoms, seek appropriate medical advice.