Let’s start with the good news—for most people living with type 2 diabetes and obesity, Mounjaro is considered safe. Like all prescription drugs, 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 you’re taking it without a prescription as a quick fix to lose a few pounds.
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 over the long term.
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 a 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, 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.
One small caveat here: 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.
The bigger caveat is that you need to use it properly. Mounjaro is only approved for certain patients (those with a BMI over 30, or a BMI over 27 plus at least one weight-related health issue). If your BMI is already in the healthy range, the medication is not licensed for you.
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.
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 the drugs haven’t been through quality control and your medical suitability might not have been appropriately assessed. It’s never worth the risk.
What are the health risks of using Mounjaro?
Like any medication, Mounjaro comes with possible health risks. Everyone will respond differently, meaning some people won’t experience any side effects at all, while an unlucky few will have a bad reaction. 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
- Feelings of malaise
- Dizziness
- Injection site reactions like irritation, itching and bruising.
Consuming a healthy diet (including regular small meals, and lots of water) 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 animal studies. We don’t currently know whether there are any thyroid risks in humans.
Who should avoid taking Mounjaro?
You shouldn’t take Mounjaro if:
- You aren’t overweight or obese—taking Mounjaro can be risky if you don’t need to lose weight
- You’re pregnant , breastfeeding, or planning to become pregnant in the near future. (People with hormonal conditions like PCOS can take Mounjaro without issue)
- You have a personal or family history of thyroid cancer
- You have multiple endocrine neoplasia syndrome type 2
- You are allergic to any of the ingredients
- You are taking any other weight loss medications
How can you take Mounjaro safely?
Stay well away from unlicensed sellers! If you’re eligible to take Mounjaro, you should start by getting a prescription from a healthcare provider. From here onwards, you’ll need to work closely with your clinician, following their advice about dosage and letting them know about any concerns.
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 may be the most effective of all.
That said, what is life-changing for one person may not be appropriate for another. That means you’ll need to talk to healthcare professionals before getting started on 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.
FAQs about Mounjaro
Is Mounjaro approved for weight loss?
Yes. Although it was first approved as a medication for type 2 diabetes, Mounjaro was also approved for weight loss in November 2023.
Is Mounjaro safe for heart patients?
Yes, Mounjaro is generally safe for patients with heart disease, and it may be beneficial.
Can Mounjaro cause thyroid cancer?
We don’t know. While Mounjaro has been shown to cause thyroid cancer in rats, there isn’t currently enough evidence to suggest it can do the same in humans.
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