Mounjaro is considered safe for people who are eligible to be prescribed it. But here’s what you should know about its potential side effects.
Let’s start with the good news—for most people, Mounjaro is considered safe.
Like all prescription medications, it has been through rigorous clinical testing, and would not have been approved for use if there were any big question marks around its safety.
This said, you may have come across some scare stories in the media. Although Mounjaro is a good choice for many people, it certainly isn’t for everyone. Using it the wrong way can be dangerous, especially if it’s not been prescribed by a registered health care professional.
Even for those who are eligible to use Mounjaro, the drug can have side effects and should only be taken under medical supervision. This article will take you through everything you need to know.
What is Mounjaro and how does it work?
Mounjaro is a weight loss treatment that reduces your appetite and helps you feel fuller for longer. You take it via injection once a week, and most people experience significant weight loss in the long term. It’s not a “magic fix” and still needs to be combined with healthy lifestyle factors, but it can be a gamechanger for some people.
Together with Wegovy and Saxenda, Mounjaro belongs to a class of drugs called GLP-1 receptor agonists, meaning it works by mimicking a naturally occurring hormone called GLP-1. Like the hormone itself, GLP-1 drugs have been shown to boost your insulin sensitivity, curb food cravings and slow down the passage of food from your stomach. Mounjaro also mimics another hormone called GIP, which seems to intensify these effects.
Is Mounjaro safe for weight loss?
Yes. Although the active ingredient in Mounjaro (tirzepatide) was first intended as a diabetes medication, it wasn’t long before the drug was approved for weight loss too. It has shown impressive results in clinical trials, eclipsing the kind of weight loss you would expect from lifestyle changes alone.
For instance, the SURMOUNT-1 trial tracked more than 2,500 eligible people over 72 weeks (around 17 months). On average, people taking the highest (15mg) dose lost 22.5% of their body weight—and 36% of this group shed a quarter of their starting weight or more.
The drug has been shown to have a good safety profile too, at least for the people it’s designed for. While side effects are common, they tend to be mild and manageable. In the SURMOUNT-1 trial, only 6.2% of people taking the 15mg dose stopped their treatment because of side effects. That means 14 people in every 15 were happy to continue.
Who can use Mounjaro?
When prescribed for weight loss, Mounjaro is licensed for use in people with a starting BMI of 30 or above, or 27 and above with at least one weight-related health condition.
But don’t worry - once treatment has started, it can continue to support you all the way to a healthier, more confident you - not just in reaching your goals, but in maintaining them too. It’s about long-term success, not just short-term change.
Safety for heart patients
Mounjaro is generally safe for patients with heart disease, such as high blood pressure, but it is not recommended for those suffering from heart failure. Research has shown that GLP-1 medications like Mounjaro may offer cardiovascular benefits for some patients, but this doesn't extend to those with severe heart conditions or heart failure.
If you have any form of heart disease, it's essential to discuss your complete medical history with your clinician before starting Mounjaro.
How safe is Mounjaro?
Mounjaro comes with possible health risks, like any medication. Everyone will respond differently, meaning some people won’t experience any side effects at all, while an unlucky few may experience more severe side effects. That’s why it’s important to take the drug under medical supervision - your doctor can help you find the right dosage and guide you towards a different medication if needed.
Mild side effects
Many people will experience mild side effects, which are generally short-lived and manageable. They tend to be most pronounced when you first start taking Mounjaro and whenever you increase your dose. Common side effects include:
- Gastrointestinal problems (burping, flatulence, constipation, diarrhoea, nausea and vomiting)
- Mild weakness or fatigue
- Dizziness
- Injection site reactions like irritation, itching and bruising.
Consuming a healthy diet (including regular small meals, and lots of water) and avoiding trigger foods that can worsen side effects can help to minimise GI problems.
Serious risks
Very rarely, Mounjaro can lead to more serious side effects such as:
- Gallbladder disorders
- Very low blood sugar
- Pancreatitis
- Allergic reactions
There has also been some speculation that Mounjaro may be linked to thyroid tumours. That’s why people with a personal or family history of thyroid cancer are advised not to take the drug. However, the precaution is based exclusively on results from animal studies. We don’t currently know whether there are any thyroid risks in humans.
Side effects support at Voy
"If you're using Voy and you experience any side effects, rest assured that our expert clinicians are just a message or phone call away. They can adjust your dose, prescribe medication to ease your symptoms, or simply offer reassurance.
Everyone responds differently to weight loss treatment and we'll help you find what feels right for you."
Is Mounjaro safe in the long term?
Mounjaro is a relatively new medication, and we don’t have much long-term data. The drug has only been on the market since 2022, with the first clinical trials conducted in 2018. However, other GLP-1 drugs have been around for 20 years, with no concerning safety issues emerging in that timeframe. If you’re taking Mounjaro, regular check-ins with your medical team are a must.
When Mounjaro might not be safe?
Moujaro safety concerns might arise if:
- You’re pregnant, breastfeeding, or planning to become pregnant in the near future. (People with hormonal conditions like PCOS can take Mounjaro without issue as long as you’re not currently planning a pregnancy)
- You have a personal or family history of thyroid cancer
- You have a history of pancreatitis
- You have multiple endocrine neoplasia syndrome type 2
- You are allergic to any of the ingredients
- You are taking any other weight loss medications
It’s also dangerous to try to speed up your weight loss by taking more than the recommended dose. All that’s likely to achieve is a double dose of side effects.
You might have heard people mention a 'golden dose' of Mounjaro, the small amount of liquid left in the pen after regular injections. While it might seem like a way to stretch your supply, our clinicians advise against using it for your safety.
Mounjaro should always be purchased from a registered pharmacy. There have been lots of reports about people buying weight loss drugs on the black market (for instance via social media or beauty salons) with serious consequences. The issue here is that you can never be quite sure what you’re getting, as our medical suitability might not have been appropriately assessed. It’s never worth the risk.
Certain medications may not be suitable while taking Mounjaro.
How can you take Mounjaro safely?
Read our guide to injecting Mounjaro safely. As discussed, you want to stay well away from unlicensed sellers when purchasing Mounjaro. And you should only take Mounjaro if it’s been prescribed by a registered clinician.
If you're planning to travel while taking Mounjaro, rest assured it’s safe with proper preparation—just follow our guide on travelling with Mounjaro for tips on storage, airport security, and more.
Is Mounjaro right for you?
If you’ve been struggling to lose weight through diet and exercise alone, the answer may well be yes. While all the new GLP-1 weight loss drugs are effective, the clinical data suggests that Mounjaro is the most effective of all.
That said, what is life-changing for one person may not be appropriate for another. That’s why it’s important to be assessed by a clinician before starting any weight loss medication.
Mounjaro isn’t the only option at Voy—find out which weight loss treatments might be right for you by filling in this short form.
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