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How much weight can you lose in a month with Mounjaro?

Robbie Puddick (RNutr)
Written by

Robbie Puddick (RNutr)

Content and SEO Lead

Dr Rachel Hall
Medically reviewed by

Dr Rachel Hall (MBCHB)

Principal Doctor

8 min read
Last updated September 2025
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Jump to: What to expect in your first month | How to maximise weight loss | Long-term expectations | Side effects during the first month | Frequently asked questions | Take home message

Most people lose between 2-4% of their body weight in their first month on Mounjaro (tirzepatide), according to clinical data from the SURMOUNT-1 trial1.

For someone weighing 100kg, that’s approximately 2-4kg (~4-8lbs). Individual responses vary significantly, with some people experiencing faster initial results while others see a more gradual start.

The pattern of weight loss in the first month often depends on your starting dose, how quickly your body adjusts to the medication, and what dietary changes you implement alongside it.

Mounjaro (tirzepatide) works by mimicking two hormones produced by the gut after eating – GLP-1 and GIP – that regulate appetite and blood sugar levels. This dual action is what sets it apart from earlier medications like Wegovy (semaglutide).

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What to expect in your first month on Mounjaro

During your first month on Mounjaro, you’ll likely experience several changes as your body adjusts to the medication:

Week 1-2:

  • Initial impact on appetite usually begin within 24-48 hours of your first injection
  • You may notice reduced hunger and food cravings
  • You’ll likely feel fuller quicker
  • Side effects like nausea or fatigue may appear (more on managing these below)

Week 3-4:

  • Weight loss typically becomes noticeable (2-4% of starting weight)
  • Some people experience the medication’s effects wearing off 4-5 days after injection
  • Hunger levels become more consistent
  • Side effects generally start to decrease

The SURMOUNT-1 trial data1 shows that while the average weight loss is 2-4% in the first month, the range varies considerably. Some patients lose as little as 1%, while others may lose 5-6% in the same timeframe.

Week Average weight loss (% of starting weight) Common patient experiences
Week 1 0.5-1% Initial appetite reduction, possible mild side effects
Week 2 1-2% Continued appetite suppression, some fluid loss
Week 3 1.5-3% More consistent effects, adjusting to new eating patterns
Week 4 2-4% Hunger levels stabilise, side effects decrease

It’s worth noting that this initial weight loss pattern is similar to other weight loss treatments and dietary interventions.

The real impact of Mounjaro becomes more apparent after three months of treatment.

First month dosing and medication effects

Mounjaro uses a titration approach, starting with a lower dose (2.5 mg) to minimise side effects before gradually increasing to a maintenance dose.

The 2.5 mg starting dose serves primarily as an introduction to help your body adjust to the medication. Most significant weight loss occurs at higher maintenance doses (5 mg, 10 mg, or 15 mg).

During the first month, the medication takes time to reach what doctors call a ‘steady state’ in your body, typically within 4-5 weeks.

Before reaching steady state, you might notice the effects fluctuate, with hunger returning 4-5 days after injection.

How to maximise weight loss on Mounjaro

While Mounjaro effectively reduces appetite and hunger on its own, research shows you can enhance your results by implementing certain strategies:

Eat a diet based mainly on whole foods

  • Ensure every meal contains a source of protein, complex carbohydrates, fibre from non-starchy vegetables, and fat
  • Include a portion of protein the size of an open hand in every meal (20-40g per meal)
  • Protein helps preserve muscle mass during weight loss
  • Practical examples: 250g Greek yoghurt (~20g protein), 4 eggs (24g protein), 100g chicken breast (30g protein)

Create a supportive food environment

  • Remove ultra-processed foods from your home
  • Prepare healthy meals in advance for busy days
  • Keep pre-cut vegetables readily available
  • Plan your meals around protein sources

Increase movement

  • Add a morning walk to your routine, even 5 minutes outside can improve our energy levels for the day
  • Consider resistance training 2-3 times weekly if able
  • Even light activity helps maintain muscle mass
  • Focus on movement you enjoy rather than intense exercise
  • Try exercise snacking, like calf raises when the kettle boils

Research from Second Nature’s programme5 shows that patients who implement these strategies alongside medication achieve better weight loss outcomes than those using medication alone.

Long-term expectations for Mounjaro weight loss

While the first month provides initial results, understanding the longer-term expectations helps put your progress in context:

Timeframe Average weight loss Research source
1 month 2-4% SURMOUNT-1 trial1
3 months 8-12% SURMOUNT-1 trial1
6 months 15-18% SURMOUNT-1 trial1
12 months 20-25% JAMA analysis2

The graph below shows the expected weight loss trajectory for Mounjaro compared to other treatments:

A graph showing the expected weight loss trajectory for Mounjaro compared to other treatments over time

Higher doses and weight loss results

Research demonstrates a dose-dependent relationship with Mounjaro, with higher doses generally producing greater weight loss1,3. A comparative analysis of the different maintenance doses showed:

  • 5 mg: Average of 7.6kg lost after 40 weeks
  • 10 mg: Average of 9.3kg lost after 40 weeks
  • 15 mg: Average of 11.2kg lost after 40 weeks

However, individual responses vary significantly. Some people achieve excellent results at lower doses, while others require the maximum dose to reach their weight loss goals.

Managing side effects during your first month

Side effects are common during the first month as your body adjusts to Mounjaro1,4. Knowing how to manage them can help you stay comfortable and adherent to treatment:

For nausea and digestive discomfort:

  • Eat smaller, more frequent meals
  • Limit ultra-processed foods and take-aways
  • Stay well hydrated (2-3 litres daily)
  • Consider ginger tea or supplements (shown to help in clinical settings)
  • Avoid lying down immediately after eating

For fatigue:

  • Ensure adequate protein intake
  • Maintain electrolyte balance by eating a diet based on whole foods (supplements not necessary unless prescribed)
  • Prioritise 7-8 hours of sleep
  • Consider timing your injection before bed if daytime fatigue is significant

In clinical trials, approximately 65% of participants experienced at least one side effect during the first month, but this dropped significantly by month three as the body adjusted1.

Frequently asked questions

Will I lose more weight if I eat less on Mounjaro?

Not necessarily. While Mounjaro reduces appetite, consuming too few calories can slow metabolism and lead to nutrient deficiencies.

Focus on nutritious, protein-rich foods rather than severe caloric restriction. Most patients naturally eat 10-20% fewer calories without counting or restricting.

Why am I not losing weight after a week on Mounjaro?

Weight loss isn’t always linear or immediate. Factors, including water retention, hormonal fluctuations, and starting at the lower 2.5 mg dose, can delay visible results.

Most people begin seeing consistent weight loss by weeks 2-3. If you’re not experiencing any weight loss or lower hunger after two weeks, discuss this with your healthcare provider.

Does weight loss on Mounjaro slow down after the first month?

For most people, weight loss accelerates rather than slows after the first month1,3. This happens because: 1) you’ll likely move to higher, more effective doses, and 2) the medication reaches steady state in your system. According to SURMOUNT-1 data, the most significant weight loss typically occurs between months 2-6.

How does the first month’s weight loss on Mounjaro compare to Wegovy?

Clinical data suggest slightly faster initial weight loss with Mounjaro compared to Wegovy (semaglutide)1,3. In the first month, Mounjaro users average 2-4% weight loss compared to 1.5-3% with Wegovy. By month three, this difference becomes more pronounced (10-12% vs 7-9%).

Will I gain the weight back if I stop after one month?

Stopping Mounjaro after just one month will likely result in regaining most lost weight, as sustainable habit changes haven’t had time to develop2.

Research shows that patients who develop healthy habits alongside medication tend to maintain more weight loss after stopping. Second Nature’s programme focuses on building these sustainable habits from day one.

How much weight do most people lose on the 2.5 mg starting dose?

The 2.5 mg dose is primarily for adjusting to the medication, not maximum weight loss1. Most people lose 2-4% of their body weight on this dose during the first month. However, individual responses vary significantly; some people are highly responsive even to the starter dose.

Take home message

Most people lose 2-4% of their body weight (roughly 2-4kg for someone weighing 100kg) during their first month on Mounjaro, with results varying based on individual factors and starting dose.

While this initial weight loss is encouraging, the most significant benefits appear after 3-6 months on maintenance doses.

Weight-loss medications work best when combined with healthy lifestyle habits. Mounjaro creates a window of opportunity where reduced hunger and cravings make it easier to establish sustainable eating patterns.

The ultimate goal isn’t just short-term weight loss but developing habits that support long-term health.

By focusing on protein-rich foods, creating a supportive environment, and increasing movement, you can maximise your results while on Mounjaro. Side effects typically improve significantly after the first month as your body adjusts to the medication.

Second Nature's Mounjaro and Wegovy programmes

Second Nature provides Mounjaro or Wegovy as part of our Mounjaro and Wegovy weight-loss programmes.

Why choose Second Nature over other medication providers, assuming you're eligible?

Because peace of mind matters.

We've had the privilege of working with the NHS for over eight years, helping people across the UK take meaningful steps toward a healthier, happier life.

Our programmes are designed to meet people where they are, whether that means support with weight loss through compassionate one-to-one health coaching, or access to the latest weight-loss medications (like Mounjaro and Wegovy) delivered alongside expert care from a multidisciplinary team of doctors, psychologists, dietitians, and personal trainers.

At the heart of everything we do is a simple belief: real, lasting change comes from building better habits, not relying on quick fixes. We're here to support that change every step of the way.

With over a decade of experience, thousands of lives changed, and a long-standing record of delivering programmes used by the NHS, we believe we're the UK's most trusted weight-loss programme.

We hope to offer you something invaluable: peace of mind, and the support you need to take that first step.

References

  1. Jastreboff, A.M., et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine, 387(3), 205-216.
  2. Aronne, L.J., et al. (2024). Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial. JAMA, 331(1), 38-48.
  3. Jastreboff, A.M., et al. (2025). Tirzepatide for Obesity Treatment and Diabetes Prevention. New England Journal of Medicine, 392(10), 958-971.
  4. National Institute for Health and Care Excellence. (2025). Tirzepatide for managing overweight and obesity (TA1026).
  5. Richards, R., et al. (2023). A Remotely Delivered, Semaglutide-Supported Specialist Weight Management Program: Preliminary Findings From a Retrospective Service Evaluation. JMIR Formative Research, 7(1), e53619.

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Write a response

Mythili

4 February, 2025

I note that you ar based in London. Do you send meds to US addresses? What would be the cost of Mounjaro for US residents?


Gerod Mitchell

28 January, 2025

I’m starting mounjaro, I’m starting at it’s lowest what should I expect if I’m working out 4 days a week and eating with a nutritionist


Henrietta Reagan

29 December, 2024

Is this a liquid form? Thank You


Robert

23 December, 2024

I’m a diabetic and have lost a lot of weight which concerns me, My question is: Can I take shots every other week as long as I keep my sugar count down.


Carol

1 August, 2024

What kind of foods can you eat by taking these shots


Shirley

14 February, 2025

Will I hav more energy


Mable Jeffries

23 May, 2024

Will these injections make your blood sugar drop like novolog does.


Barbara Stoddart

24 January, 2025

I used to take Trulicity which I was able to get on prescription. But then it became unavailable. I felt good on this but for twelve months without it I felt unwell and my glucose shot up regardless of keeping to a good diet and taking insulin. Thankfully my diabetic team were able to get this Mounjaro I’m able to have this on prescription. What a difference. Within days my glucose went down and I’m starting to feel my old self again. Hopefully I’ll beable to continue with this.
It’s well worth it. X


Karen Jenkins

1 August, 2024

Yes mine definitely did I’m only on the lower dose of mountain and my blood sugar has come down drastically


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