How long before Mounjaro starts working? A guide to early effects and outcomes

You’ve committed to using Mounjaro to fuel your weight loss journey, but you’re curious how long the whole thing will take. Or, perhaps you’re already injecting it but still not seeing much progress.

How long does Mounjaro take to work? Could it be days, weeks or even months until you notice results, or should you be losing weight straight away?

The good news is that Mounjaro starts working fairly quickly. However, there are several factors that can impact your weight loss timeline, as well as a few things you’ll need to do to ensure you get optimal results.

Here’s the lowdown.

What is Mounjaro and how does it work?

Mounjaro is an injectable medication used to treat type 2 diabetes and weight management. It uses the active ingredient tirzepatide, a dual-agonist that mimics GLP-1 and GIP hormones to regulate blood sugar levels and appetite. As far as weight loss is concerned, Mounjaro reduces appetite and slows gastric emptying, making you feel fuller for longer.

Mounjaro works on a progressive schedule, where you start with a fairly low dose of 2.5mg and gradually work your way up to higher doses before settling on a maintenance dose. You increase your dose at least every four weeks. 

Mounjaro might sound a lot like other weight loss injections such as Ozempic and Wegovy, but its key difference is the dual-action mechanism. While Mounjaro targets both GLP-1 and GIP hormones, Ozempic and Wegovy act only on GLP-1 receptors. In many cases, this makes Mounjaro more effective for weight loss [1].

Does Mounjaro work immediately?

Technically, yes. Mounjaro starts working almost as soon as you take your first dose. Within just a few hours, it begins regulating your appetite and blood sugar levels, and slowing gastric emptying. However, you won’t be able to see visible results for a while longer. 

This is intentional. Mounjaro isn’t an instant solution, but a long-term weight management medication that delivers the best outcome over an extended period.

How long does it take for Mounjaro to work?

Visible weight loss doesn’t really kick in for at least several weeks. This is because your body needs adequate time to adjust to the medication, and you need to be in a calorie deficit for a sufficient amount of time before your body starts losing fat. 

Weight loss happens when your body burns more energy than it consumes. Mounjaro helps the process by curbing your appetite, reducing cravings and making you feel fuller for longer, making it much easier to reduce your calorie intake. When you eat fewer calories, your body then turns to alternative energy sources. First, your natural glycogen stores (your body’s primary energy source), then body fat. 

A consistent calorie deficit means your body is repeatedly using fat for energy. After a few weeks, you might notice some weight loss, and then even significant weight loss after a few months.

Several studies back up this timeline. For instance, a 2022 study found that Mounjaro patients start losing weight in the first four weeks, and drop about 6% of their body weight after eight weeks and 8% after 12 weeks. 

Over 72 weeks (roughly 16.5 months), patients could lose up to 22.5% of their initial body weight when they reach the maximum Mounjaro dose of 15mg [2].

Remember, though, that results are incredibly individual. While one person might begin losing weight rapidly, another might take months. There are lots of factors that influence how much weight you lose and how quickly, so the best thing to keep in mind is that you’re on your own journey, and your weight loss progress should always be celebrated – no matter how soon it comes.

Week-by-week results: What to expect on Mounjaro

Here’s what you might experience week-by-week on your Mounjaro journey.

Week 1

You’ll begin on the lowest dose of 2.5mg. The medication will start working very soon after you first take it, and you may notice that you’re suddenly not as hungry, feeling fuller for much longer than you’re used to or not craving the same foods.

You’re unlikely to notice dramatic results just yet, but your body may lose water weight because you’re taking in fewer calories and your body is burning through glycogen stores. Once it’s exhausted these, it turns to fat for energy instead, which is when real weight loss happens.

It’s important to note that you may also experience common Mounjaro side effects like nausea, constipation and fatigue when you first take the medication. These may subside as your body adjusts, but if you’re struggling, don’t hesitate to reach out to your GP or healthcare provider.

Weeks 2-4

You’ll stay on the 2.5mg weekly dose for at least four weeks. Because you’ve been using it consistently, you’ll likely notice the appetite-reducing and digestion-slowing effects of the medication.

During this time, your body might also switch to fat as its primary fuel source, leading to genuine fat loss. That same 2022 study found that in the early weeks, Mounjaro users lose just under 1% of their initial body weight per week [2].

And if you’ve been experiencing side effects, you may find these ease around now.

Weeks 5-8

Week 5 is when you up your dose to 5mg. Increasing your dose can help fuel your weight loss efforts, with most patients feeling greater appetite reduction and longer-lasting fullness when they move to the higher dose. By now, many patients have lost about 5-6% of their starting body weight (although results can vary).

However, a higher dose can also make those unpleasant side effects reappear, albeit usually only temporarily. Once again, they should subside as your body adapts, but if they’re severe or persistent, chat to your doctor. They might advise reverting to the lower dose for longer so your body has a better chance of adjusting.

Weeks 9-12

Many patients lose up to 8% of their initial weight by this point. If they’re satisfied with their results, they might stick to 5mg as their maintenance dose – the dose you might continue taking long-term to sustain your weight loss efforts. 

If you’re keen to keep going and your body is tolerating your current dose, you’ll increase your dose again at the 9-week mark, this time to 7.5mg weekly. The new dose may lead to the temporary return of side effects, but these will hopefully be temporary.

Weeks 13-16

This is when you’d switch to the next-highest dose of 10mg. By now, you might have lost more than 10% of your starting weight.

10mg is another Mounjaro maintenance dose, so if you find that this amount is sufficient for maintaining your weight, you might remain on it long term.

Weeks 17-20

Some patients go up again to 12.5mg weekly doses. They might lose even more weight and experience more pronounced appetite-controlling effects.

Weeks 21 and beyond

At this point, you’d get to the maximum dose of 15mg. Appetite suppression is at its strongest point now, meaning you’re likely consuming far fewer calories and experiencing fewer cravings.

For many patients, 15mg is the maintenance dose they’ll settle on. But it doesn’t necessarily mean you’ll be on it forever; if you’ve reached your goals and you’re keen to come off the medication, your doctor can put together a tapering plan to stop taking it safely.

Factors that affect how quickly you lose weight on Mounjaro

Mounjaro can be effective, but many different factors impact its success:

• Starting weight: If your starting weight is higher, you may experience more noticeable weight loss early on
• Dose level and schedule: Weight loss is typically more pronounced at higher doses, so if you’re staying on lower doses for longer than the standard four weeks, results may be slower
• Body’s response: Some patients notice a greater effect on their appetite quite quickly, while others might not experience it until they reach a higher dose
• Diet: Sticking to a nutritious, reduced-calorie diet may speed up weight loss, while continuing a high-calorie one can delay your progress
• Exercise: Regular exercise can boost your weight loss efforts, potentially helping you lose body fat more quickly
• Side effects: If you experience side effects, you may be more likely to stay on a lower dose for longer, possibly delaying your results
• Existing health problems: Certain medical conditions may make it harder for your body to lose weight, including PCOS, hypothyroidism and insulin resistance

Why am I still hungry on Mounjaro?

Even though Mounjaro is designed to suppress your appetite, you might still be experiencing hunger. This is totally normal. Your body will still get hungry (and it should) – Mounjaro simply reduces the intensity and frequency.

But if your hunger hasn’t changed since you started taking the medication, there could be multiple explanations:

• Your dose isn’t high enough: Some patients find that a particular dose isn’t having enough of an effect on their appetite, which is why they move up to a higher one. They might also stay on a particular dose for too long, allowing their body to effectively build up a tolerance towards it. In either case, moving up to a higher dose could help reduce hunger further.
• You’re eating low-nutrient foods: Nutrient-dense foods help you feel fuller for longer, while refined carbs and high-sugar and high-fat foods can lead to blood sugar fluctuations and hunger soon after eating. It could be that even though you’re eating less, you’re focusing on the wrong foods.
• You’re eating for other reasons: You might not be hungry, but instead eating for other reasons – this is known as emotional eating. If you’re upset, stressed or even bored, you might turn to food to soothe your emotions, even if you’re not experiencing real physical hunger cues.

How to get the best results from Mounjaro

Here’s how you can maximise your results when taking Mounjaro:

• Stick to the dosing schedule: It might be tempting to jump to the next-highest dose as soon as possible, but there’s a reason the dosing schedule exists: it helps your body adjust to the medication to give you the best possible chance of success. Following the recommended dosing schedule can help ensure you lose weight safely, not rapidly.
• Be consistent: Try to take Mounjaro at the same time on the same day each week. This can make the medication more effective, as you’re keeping a consistent level of it in your body.
• Optimise your diet: Pack your diet with nutrient-dense whole foods, like vegetables, fruits, lean proteins, whole grains and healthy fats. Limit your intake of sugary, high-fat and ultra-processed foods, which can hamper your efforts.
• Maintain a regular exercise routine: Exercise is crucial for burning calories, building muscle and boosting your energy levels. If you can, aim to incorporate both cardio and strength training into your weekly routine. Every bit counts, so move your body as much as possible each day – even if it’s just a walk around the block!
• Stay hydrated: Water helps to support your metabolism and digestive system, plus it may alleviate some of the side effects associated with Mounjaro. Drink between six and eight glasses each day.
• Target emotional eating: If you’re eating when you’re stressed, upset or even bored, pinpoint the triggers and address them. This is called mindful eating; it means paying attention to your body’s signals, identifying genuine hunger cues and stopping when your tummy is full.
• Know how to manage side effects: If you do experience side effects at any point, there are some things you can do to alleviate them. Eat small, plain meals if you’re nauseous or vomiting; rest as much as possible; try a natural remedy for digestive symptoms; or reach out to your GP or healthcare provider if side effects don’t go away or feel unmanageable.
• Keep a long-term focus: Above all, keep in mind that Mounjaro is a long-term treatment, not a quick fix. While you might not see results straight away, it’s important to stay with it and be patient.

Access Mounjaro for weight loss (and much, much more)

Thinking of kickstarting your weight loss journey with Mounjaro?

Juniper's Weight Loss Reset Programme combines weight loss medication with dietitian-led health coaching and tracking, so you can lose weight and reach your goals for good.

Kickstart your weight loss journey with Wegovy or Mounjaro, two groundbreaking weight loss medications that mimic the GLP-1 and GIP hormones, respectively, to help control cravings, delay stomach emptying, and keep you feeling fuller for longer. These clinically backed treatments help members experience up to 20% body weight loss.

Plus, we have a team of expert dietitians and health coaches you can consult with to help you work through any challenges you're experiencing during your weight management journey. This approach sets you up for sustained weight loss, rather than a quick-fix solution.

This means you can continue to enjoy the things you love in moderation without ever feeling deprived.

Ready to see if Juniper is right for you? You can check your eligibility here.

All in all, joining Juniper makes you 4.5x more likely to lose significant weight than using medication alone.

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