Why am I not losing weight on Mounjaro?

Mounjaro is a popular weight loss drug, but may not always have its desired effect. Here’s what may be wrong if you aren’t losing weight on Mounjaro
Habitual Team
min read
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Quick summary

If you're taking a weight loss medication like Mounjaro, you may have already lost a significant amount of weight. But if you've stopped losing weight, you're probably wondering why that is, and what can be done about it.

Losing weight on Mounjaro isn’t as simple as taking the injection weekly—there are many other factors at play, whether that’s your overall approach to your health and lifestyle decisions, your existing health conditions, or otherwise. Crucially, taking Mounjaro isn’t a magic pill, it’s more complex than that. 

There are a number of reasons you may not be losing weight while on Mounjaro—here are a few of them.

You’ve hit the weight loss plateau

Few weight loss journeys, if any, are linear. Rather, you should think of weight loss more like a rollercoaster, where progress may be staggered and your weight may even go up and down. 

A fairly common phenomenon is that of the weight loss plateau, which, as the name suggests, is when you stop losing weight and your weight levels out. There is a scientific reason for this: when your body can sense you are losing weight, it responds by lowering your metabolism in order to try and store fat and adjust the ‘set point’ (the desired level of stored fat in your body). [1]

This tends to last for 8 to 12 weeks, and may even see you start to regain weight before you start losing it again. 

There are a number of ways to break through the weight loss plateau. Increasing the amount of exercise you are doing (including more resistance training) can help, as can decreasing the amount of carbohydrates you’re eating and replacing them with proteins. 

You’re not sticking to the advised dosage

If you’re taking Mounjaro, you’ll start your course of medication at a low titration (2.5mg) in order to minimise any of the more intense side effects you may experience as a result of the drug. Over time, your titration should increase, so that the medication can have its maximum impact.

One reason why you may not be losing weight is that you are missing your dosage regime (e.g. not taking it once a week as required). It’s okay if you miss one dose, as long as you take it within reasonably close proximity to when it was required, and not too close to your next dose. The best way to avoid this is having a set time every week (e.g. Wednesday lunch time) when you take your medication, and sticking to it. 

It also may be that you haven’t increased your dosage up to the higher level (5mg). This is standard practice after being on the lower dosage for the first four weeks, so you should be able to increase it with a relative degree of confidence. Only if you start experiencing adverse side effects should you move back down to the lower concentration. 

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Lifestyle habits

If you do make the mistake of considering Mounjaro as a ‘magic pill’ cure, you may be neglecting the fact that you need to make changes across your lifestyle in order to see any real weight loss progress. 

Diet is critical to this. While we might not recommend calorie counting, you should consider whether you are eliminating unnecessary calories out of your diet to help you lose weight. You should be eating plenty of vegetables, more complex carbohydrates (wholewheats, brown rice, etc), and drinking plenty of water. 

Protein should be a key part of your diet, as it boosts your metabolism and helps you build muscle mass. So it may be that you aren’t eating enough protein—so pad out your meals with lean meats (like poultry, fish) eggs, dairy products, legumes, and tofu.

Exercise too plays a big part. A regular routine of exercise is central to any weight loss journey, with at least 30 mins a day, five days a week. Many recommend resistance training (any exercise that helps you build muscle mass while working out) as it helps you increase the amount of calories you burn as you are exercising. [2]

When you do stop losing weight, it is often tempting to slip back into old habits, often out of frustration or to comfort yourself. It’s important to remain resolute and see this as part of the journey and something that is within your control to change.  

Your starting weight

One other reason that Mounjaro may not be having its desired effect is related to your starting weight. It’s worth remembering that Mounjaro is designated for people who are overweight or obese, and will therefore have a higher starting weight. 

People with a lower starting weight will simply not experience the same benefits of weight loss, and therefore are not recommended to take medications like Mounjaro. 

Underlying health conditions

There are certain underlying health factors that may mean your body doesn’t lose weight as a result of medication like Mounjaro. As with most medications, there is a category of ‘non-responders’, a percentage of people for whom the medication has negligible effect.

On trials for tirzepatide (the scientific name for Mounjaro), 85% of patients lost 5% of their body weight on a dose of 5mg. That means for 15% of patients, the drug had no impact. There are of course other factors at play here, but that shows there is a percentage of people who will not respond to the drug. [3]

With any weight loss drug, if you are finding the medication to be ineffective, it always benefits from speaking to a health professional. Ultimately, they will be best positioned to understand the factors that may be influencing if you are losing weight or not, and how to proceed.

How Habitual can help

Lifestyle changes are key to sustained weight loss. A healthy balanced diet and regular exercise need to form part of your approach alongside taking Mounjaro. Habitual make create positive habits easier with daily tracking and motivation, a progress dashboard, 1:1 patient support, peer support groups, expert-written content, recipes, and rewards. View our plans to learn more.


[1] Willner, T. (2023). Weight-loss plateaus explained, Second Nature, retrieved December 4th 2023.

[2] Hunter, G., Byrne, N., Sirikul, B., et al (2008). Resistance training conserves fat-free mass and resting energy expenditure following weight loss, Obesity (Silver Spring), May 2008, 16(5). Accessible here

[3] Jastreboff, A, Aronne, L., Ahmad, N. (2022). Tirzepatide Once Weekly for the Treatment of Obesity, N Engl J Med 2022; 387:205-216. Accessible here

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