Mounjaro Weight Loss: Week by Week Guide

Losing weight can be a challenging prospect that’s deeply personal for each individual. There’s no one-size-fits-all solution, with everyone’s journey being completely different. While some can achieve their goals through diet and exercise alone, others may need the additional support of specialist medications.

Mounjaro is one of these treatments. It’s a self-injectable solution which contains the active ingredient, tirzepatide, and can produce some impressive results — with research showing it is possible to lose up to 22.5% of your starting body weight after 72 weeks of treatment on its highest maintenance dose.

If you’re thinking about incorporating medication into your own routine, you will probably want to know what Mounjaro weight loss could look like on a week-by-week basis. In this article, we’ll guide you on what to expect on our journey, the latest clinical research, potential side effects, and much more. Let’s get started. 

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Starting Mounjaro: Mounjaro Week 1

Everyone will begin their Mounjaro weight loss journey on the lowest dosage of tirzepatide, even if they've used the treatment in the past or are switching from a different medication. Starting on a low dose of Mounjaro and gradually increasing the strength over many weeks will help lower the risk of side effects. If your body tolerates Mounjaro well, you’ll follow this schedule until you reach the maximum maintenance dose: 

Before you inject Mounjaro for the first time, we suggest reading our ‘How to use the Mounjaro injection pen' guide. You will also need to:

• Choose a suitable day and time to inject yourself – this will remain the same each time 
• Decide on an injection site – pick from the thighs, abdomen, or upper arms and rotate each week

Mounjaro Week 1 Weight Loss 

Mounjaro weight loss will not happen overnight, and the effects in week one can vary from person to person. Some people may experience a rapid drop in weight, moderate weight loss, or very little to nothing at all. A sudden loss of weight early on in your journey can be due to the body expelling water. When you eat fewer calories, your body releases glycogen, your stored energy, to replenish the energy it’s not getting. Because every gram of glycogen is stored with 3g of water, when the energy is released, so too is the water, which will leave your body as waste in urine, stools, and sweat.

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Clinical trials have reported that people using Mounjaro typically feel less hungry, so you should start to notice changes to your appetite within the first week of treatment. This reduction in appetite can help to put you in a calorie deficit, where you eat fewer calories than you are burning, setting you up for your weight loss journey.

Side Effects

You may also experience some Mounjaro side effects. These should be mild and can be a sign that your body is adjusting to the new medication. They should subside over time, but can include:

• Feeling sick
• Diarrhoea
• Constipation
• Stomach cramps
• Headaches

If you find the Mounjaro side effects particularly bothersome, you can remain on the current dose longer to allow your body more time to get used to the medication. You should discuss this with the clinician, who will help tailor your dosage schedule if needed. 

Mounjaro Tips for Week 1

Because side effects are more common during the first week of Mounjaro treatment, there are things you can do to make the first week (and beyond) more manageable, such as:

• Eating a balanced diet that incorporates plenty of fruit, vegetables, and whole grains - check out our 7-day diet plan for weight loss
• Avoiding skipping meals – if you are feeling unwell, choose bland or easy-to-digest foods, such as soups, until it passes
• Staying hydrated by aiming to drink six to eight glasses of water per day; this will help manage side effects and prevent dehydration
• Starting an exercise routine to complement the effects of Mounjaro
• Familiarising yourself with the Mounjaro patient information leaflet
• Avoiding being too hard on yourself; it is only the first week, and it can take a few weeks for you to notice the full benefits

Mounjaro Week 2

As you enter the second week, you may feel similar to the previous one. The Mounjaro dose will remain at 2.5 mg, so the effects may become stronger, both for weight loss and side effects. However, some people find side effects begin to ease at this time, too. If you’re having difficulty or are really struggling, contact your clinician for advice

It’s important to continue with your diet and exercise plan during this week to help increase the effectiveness of Mounjaro and to build healthy habits. 

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Mounjaro Weeks 3 and 4

After three-to-four weeks of Mounjaro treatment, many people notice their side effects easing. You should continue on the starting dose of 2.5 mg each week.

Research shows that after four weeks of tirzepatide treatment, participants lost around 4% of their starting body weight. You may lose more or less than this amount, but the best way to ensure Mounjaro is effective is to follow a calorie-controlled diet and exercise regularly.

This will be made easier by the fact that your appetite may be reduced and you notice you are eating less than you did. However, it is important that you don’t skip meals and adopt healthy lifestyle practices to prevent future weight gain, even after you stop Mounjaro treatment.

Mounjaro Weeks 5 to 8

It’s time for your first dose increase. In week 5, if you have tolerated the starting Mounjaro dose well, you will step up to 5 mg of tirzepatide each week for the next four weeks. 

Weight Loss Expectations 

During this time, an average weight loss of up to 6% is common. However, don’t worry if you are above or below this figure; this is just an average. Try to refrain from weighing yourself regularly. You should weigh yourself every 2 to 4 weeks, as your weight can fluctuate daily because of several factors, including water retention. You might notice some of your clothes fit differently now, which can also be a sign of weight loss. 

The Return of Side Effects?

An increase in dose at week 5 can mean your side effects come back because your body will need some time to adjust. As before, these will likely disappear on their own, but if they are severe or are not going away, the clinician may suggest remaining on the starting dose for a while longer. If the effects impact your quality of life, you may need to consider an alternative weight loss treatment. 

How You Might Feel

Now that you’ve experienced your first Mounjaro dose increase, you may notice you feel fuller after meals and less hungry, making it easier to stick to your diet plan.

It’s important to continue with your exercise regime as this will help with reaching your weight loss goals faster. You’ve probably noticed that you have more energy and feel better in yourself, and this will only keep getting better as your journey continues.

Mounjaro Weeks 9 to 12

Week 9 is the start of another dose increase. This time, you should increase to 7.5 mg of tirzepatide each week for the next four weeks. Studies show that participants can lose up to 8 to 9% of their total body weight at this point.

Here, many users report major changes in their relationship with food, with cravings becoming less intense. You may even notice visible changes to your appearance, your clothes may fit differently, and you should have more energy.

If you haven't already, now is an excellent time to incorporate strength training into your routine. As you lose fat, preserving muscle mass will help you stay toned. It can also help to combat loose skin.

Managing Mounjaro Side Effects

Another dose increase can leave you susceptible to side effects. If they do return, it can help to adjust your lifestyle when your dose increases by:

• Eating, smaller, more frequent meals, switching from three large meals to five small meals per day can help
• Drinking plenty of water to manage side effects and prevent dehydration
• Getting plenty of rest
• Taking over-the-counter medications to combat diarrhoea, acid reflux, or constipation
• Incorporating more fibre into your meals to aid digestion, keep you feeling fuller, and prevent constipation
• Continuing with exercise

If you don’t feel ready to increase your dose at this point, speak to your clinician. Remember, your weight loss journey with Mounjaro is unique to you, so if you are experiencing side effects or are losing weight with your current 5 mg weekly dose, it may be possible to stick with your current strength.

Mounjaro Week 13 Onwards

From week 13, the Mounjaro dose can increase to 10 mg per week. The average weight loss after three months of using tirzepatide is about 8%.

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At this point, as long as you have lost at least 5% of your starting body weight on Mounjaro, your clinician will recommend that you continue with your treatment.

As you increase your dose, you may experience some Mounjaro side effects, but these can be managed as you have been and should wear off as your body adjusts to the increase. 

Increasing to the Mounjaro Maintenance Dose

If all goes to plan, you will continue increasing your dosage, under the supervision of your clinician, every four weeks by 2.5 mg. That means you should reach the maximum Mounjaro maintenance dose of 15 mg per week on week 21.

The maintenance dose is the strength you will remain on for the duration of your treatment. If you have remained on the lower doses for longer, then it will take longer than 21 weeks to reach the highest maintenance dose. You may not even reach this strength if you’re having success with a lower amount.

Remember, this is your weight loss journey and how your body responds to treatment, how long it takes to lose weight, and the amount you lose will be unique to you.

How Much Weight Can I Lose on Mounjaro?

Mounjaro isn’t a quick fix for weight loss and is intended to be a long-term treatment that is most effective when used alongside healthy lifestyle choices. Research shows that after 72 weeks at the highest maintenance dose of 15 mg per week, Mounjaro can help you lose up to 22.5% of your initial body weight.

The results from the SURMOUNT-1 study are shown on the graph below, but can be summarised as follows. After 72 weeks of Mounjaro treatment, study participants lost 16% (5 mg/week), 21.4% (10 mg/week), and 22.5% (15 mg/week) of their starting body weight.

This is compared to just a 2.4% body weight loss in people prescribed a placebo. The results also show that 89% of people on the 10 mg dose and 91% of those assigned the 15 mg/week dose lost at least 5% of their starting body weight. A weight reduction of 5% is believed to have a clinically meaningful effect on metabolic health. 

Overall, the average reduction in fat mass was 33.9% in the Mounjaro group compared to 8.2 % with a placebo. The weight loss associated with Mounjaro was also associated with bigger improvements in heart and metabolic risk factors, including:

• Blood pressure
• Waist circumference
• Insulin sensitivity
• Blood fat levels

How to Increase Weight Loss on Mounjaro 

Mounjaro won’t be as effective on its own, so you’ll need to commit to changing your lifestyle to accompany the weight loss medication. Some of the things you can do are:

1. Follow a balanced diet
2. Exercise regularly
3. Practice good sleep hygiene 
4. Manage stress
5. Rotate injection sites
6. Be patient

Let’s take a look at the points in more detail:

Follow a Balanced Diet

Diet is crucial for weight loss, with or without medication. It is important to focus on whole foods, like fruit, vegetables, wholegrains, and lean proteins while restricting your intake of processed foods and sugary or fizzy drinks. A healthy, balanced diet will not only encourage weight loss but will also ensure you’re getting all the nutrients you need to stay healthy. Here are some of the foods you should avoid while using Mounjaro.

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Exercise Regularly

Regular exercise keeps your energy levels in balance. Consuming too many calories and not burning enough off contributes to weight gain. Adults should aim to complete at least 150 minutes of moderate-intensity exercise each week. It’s also important to incorporate strength-based activities on two days each week to stop you from losing muscle mass as you lose weight. 

Practice Good Sleep Hygiene

Sleep is a really important factor for weight loss. Without adequate sleep, you’re more likely to crave food and snacks, contributing to weight gain. Sleep deprivation also increases cortisol levels, a stress hormone, which can alter your appetite. You can help by aiming to get seven to nine hours of sleep by night and practising good sleep hygiene, such as:

• Setting a bedtime routine, e.g. going to bed and waking up at the same time each day
• Ensuring your room is clean, cool, dark, and quiet
• Changing your bedding regularly
• Avoiding napping in the afternoon and evening
• Not using screens up to two hours before bed

Manage Stress

Stress is a hindrance to weight loss and leads to an overproduction of cortisol, increasing your appetite. Manage stress with hobbies, meditation, mindfulness, and spending time with friends and family.

Mounjaro

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• Approved Weight Loss Treatment
• Suitable for adults with a BMI of +30kg/m²
• Pre-filled injection pen

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• Discreet delivery next working day
• Online prescription - No doctor visit

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Rotate Injection Sites

If irritation or inflammation around your injection sites is making you dread your next Mounjaro dose, it could be because you’re not rotating the site regularly. The three areas where you can inject Mounjaro are your:

• Thighs
• Abdomen
• Upper arms

You should rotate your injection sites around these areas each week or divide each section into four and move around these weekly. This will minimise irritation and make self-injection more comfortable.

Be Patient

Just because research shows Mounjaro can help you lose up to 22.5% of your body weight in 72 weeks at the highest maintenance dose, this does not mean your own journey will follow the same path.

Set a target for how much weight you want to lose, with smaller, realistic goals in between, but don’t be too harsh if you don’t meet them the first time. If you need further support or advice, you can contact your clinician at any time. 

Start Your Mounjaro Weight Loss Journey with Prescription Doctor

Now that you have an idea of what Mounjaro weight loss could look like on a week-by-week basis, you may feel ready to take the first step on the journey. If that’s the case, Prescription Doctor is here to help.

We’re committed to taking the hassle out of healthcare, which is why we provide a smooth ordering process that includes fast and discreet delivery. With us, there are no awkward conversations with GPs to worry about, just a simple online questionnaire to assess your suitability for the medication. Once completed, you could receive your order the very next day — it’s that straightforward.

Prescription Doctor has been supporting people just like you since 2013, meaning we’re perfectly placed to help you kick-start your weight loss journey in the most efficient way. We only stock UK-licensed and approved medications, while our dispensing pharmacy is fully-regulated by the General Pharmaceutical Council (GPhC), so you can be completely confident in the quality of our products and service.

Begin your weight loss consultation with us today and get started on your journey.

Frequently Asked Questions

How Long Does Mounjaro Take to Work?

The active ingredient in Mounjaro, tirzepatide, starts working from the first week of treatment, but how much weight you will lose in a month with Mounjaro is unique to you. Some people experience some weight loss and appetite changes straight away, whereas it can take a few weeks for others to see noticeable differences. 

How Much Weight Will I Lose in the First Month of Mounjaro Treatment?

Research shows that you can lose up to 4% of your starting body weight in the first month of Mounjaro treatment. However, this is an average, so this may be different for you. You can support the effectiveness of Mounjaro for weight loss by sticking to a diet and exercise plan.

Why Am I on Mounjaro and Not Losing Weight? 

Several factors could be contributing to slow or no weight loss with Mounjaro, including:

• Dosage: if you haven’t yet reached the maintenance dose or you’re not taking the medication consistently, this could be why you are not losing as much weight as you’d like.
• Diet: Mounjaro works best when it is combined with lifestyle changes, including diet. It’s important you are eating the correct amount of calories and the right foods.
• Exercise: if you’re not exercising enough, then you won’t lose weight with Mounjaro.
• Time: the medication may need more time to work, especially if you are still within the first 12 weeks of treatment.
• Medications: ask for a medication review with your clinician to see if any of your other medications could be contributing to weight gain. 
• Plateau: you may have reached a weight loss plateau, read more about them in our guide ‘Stages of noticing weight loss’.

Authored By

Leanne Edermaniger

Medical Content Writer

Leanne is a science and health content writer focusing on human health and biology while utilising her solid academic background.

Published on: 22/07/2024

Reviewed By

Mohamed Imran Lakhi

MPharm - Lead Pharmacist

Imran Lakhi is the superintendent pharmacist and founder at Prescription Doctor. He has been at the core of our team.

Reviewed on: 07/04/2025