Is Mounjaro® Safe? Side Effects & Long-Term Safety
Key takeaways:
Mounjaro® is safe for many people.
It can help with weight loss and long-term weight management, improving health in many ways.
Mounjaro® side effects are usually mild to moderate (nausea, vomiting, diarrhoea, constipation, etc.) and get better over time.
Serious side effects include problems with the pancreas and gallbladder, but these are rare.
Mounjaro® (tirzepatide) is licensed in the United Kingdom to help people with type 2 diabetes manage their blood sugar levels, as well as people with obesity and overweight lose weight.
If you have overweight or obesity, Mounjaro® can help you reach a healthy weight, maintain that body weight, and improve your overall health.
But is Mounjaro® safe? Research shows Mounjaro® is safe for many people. The most common side effects are mild-to-moderate gastrointestinal effects, like nausea or vomiting. These typically get better with time.
Read on for more on Mounjaro® safety, including the common side effects, rare long-term risks, and how to use the weight loss injection safely.
Is Mounjaro® Safe?
Mounjaro® is safe for many people. This dual GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) receptor agonist is a prescription medicine, so you can only get it if a healthcare provider thinks it’s safe for you.
Your GP (general practitioner) or a private clinician will look at your medical history, body mass index (BMI), current health, and any medications you’re already on to determine if you’re a good candidate.
Since Mounjaro® can help you lose weight and maintain that lost weight, it can improve your health in many ways and reduce the chances of obesity-related health conditions.
Obesity can increase the risk of:
Type 2 diabetes
Heart disease
High blood pressure (hypertension)
Stroke
Mental health issues
Some types of cancer
So, the benefits of taking Mounjaro® outweigh any potential risks for many people.
It’s licensed by the Medicines & Healthcare products Regulatory Agency (MHRA) for type 2 diabetes and weight loss. The National Institute for Health and Care Excellence (NICE) recommends Mounjaro® for the management of obesity.
Studies on the Safety of Mounjaro®
Many clinical trials on Mounjaro® show that the medicine is safe for many people.
For example, a 2022 study looked at more than 2,500 people taking different doses of Mounjaro® or a placebo. There were no major safety concerns, and the most common side effects were mild-to-moderate gastrointestinal effects, like nausea and vomiting.
After 72 weeks of taking Mounjaro® and making lifestyle changes, people taking a 15-mg (milligram) dose lost an average of 23.6 kg (kilograms), about 3.7 stone.
Plus, a 2025 narrative review looked at 17 studies on tirzepatide — the active ingredient in Mounjaro® — and people with obesity but not type 2 diabetes.
It concluded that the medicine can lead to significant weight loss, cardiometabolic benefits, and improved quality of life, and that tirzepatide had a favourable safety profile.
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Common Side Effects of Mounjaro®
Just like any medicine, Mounjaro® comes with possible side effects.
The most common side effects of Mounjaro® include:
Nausea
Diarrhoea
Vomiting
Constipation
Stomach pain
Mounjaro® side effects are usually mild or moderate. You might experience them when you first start taking the medicine and when your dose increases, which it does every four weeks at the start of your treatment.
The good news is that side effects tend to get better with time as your body gets used to the medication.
Long-Term Safety of Mounjaro®
Mounjaro® has a few more serious, potential side effects, though these are rare.
Long-term risks of Mounjaro® may include:
Inflammation of the pancreas (pancreatitis)
Gallstones
Inflammation of the gallbladder
Low blood sugar (hypoglycemia) if you have type 2 diabetes
There’s also a risk of an allergic reaction.
Studies on rats found that Mounjaro® can cause thyroid C-cell tumours, but it’s unclear if this can happen in humans. Research so far hasn’t found a link between tirzepatide and an increased risk of cancer.
Let a healthcare professional know if you experience any serious side effects or if anything feels off.
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How to Use Mounjaro® Safely
To use Moujaro® safely, make sure you follow any instructions from your GP or private healthcare provider. They’ll likely prescribe Mounjaro® alongside healthy eating and physical activity as part of a wider weight loss treatment plan.
Follow these general steps to stay safe on Mounjaro®:
Take Mounjaro® once a week. You should inject Mounjaro® once a week into your stomach, thigh, or upper arm on the same day each week. Rotate your injection site each time to avoid irritation.
Stay hydrated. This is especially important if you’re sick or have diarrhoea. Set reminders if you forget to drink water, and take small sips throughout the day.
Follow your dose-escalation plan. Your clinician will prescribe a low dose of Mounjaro® that slowly increases every four weeks. Gradually increasing your dose like this can reduce the chances of side effects.
Let your clinician know about troubling side effects. They may want to lower your dose or keep you on your current dose for longer before increasing it. This gives your body more time to adjust.
Avoid triggering foods. You might find that fatty, greasy, or fried foods trigger nausea or other gastrointestinal side effects.
Is Mounjaro® Safe? In Summary
Mounjaro® is considered a safe medicine for many people. For those with obesity or overweight, it can be a useful tool to help with weight loss and weight management.
Here are the key points to bear in mind:
Mounjaro® side effects are mostly gastrointestinal. You might experience nausea, vomiting, and diarrhoea. Side effects tend to be mild to moderate and get better with time.
Rare side effects exist, as with any medicine. Rare adverse effects may include pancreas and gallbladder problems. Let your GP or private clinician know if you experience any worrying symptoms.
Mounjaro® benefits may outweigh potential risks. The medicine can help you reach a healthy weight, which can reduce the risks of several health problems.
Of course, we all react to medication differently, and many factors determine whether a medicine is right for you or not. A GP or private healthcare provider can go over the details and let you know if Mounjaro® is a safe choice for you.
You can learn more about your weight loss medication options through the Hers U.K. platform.
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FAQs
See answers to common questions about the safety of Mounjaro® below.
Is Mounjaro® safe while pregnant?
It’s unknown whether Mounjaro® is safe while pregnant, so the current guidance is to not take the medicine during pregnancy. Stop taking Mounjaro® at least one month before trying for a baby. Let your GP or private clinician know if you get pregnant on Mounjaro® or would like to try to conceive soon.
Is Mounjaro® safe while breastfeeding?
It’s unknown whether Mounjaro® is safe while breastfeeding, so the current guidance is to not breastfeed while taking the medicine. Your GP or private clinician can tell you if it’s better to avoid Mounjaro® or stop breastfeeding, based on your health needs.
Who should avoid Mounjaro®?
You should avoid Mounjaro® if you’re pregnant or allergic to any ingredients in the medicine. Let your GP or private provider know about any medical conditions you have or medications you’re taking. They may want to monitor you more closely if you have, for example, severe gastrointestinal disease or a history of pancreatitis.
What are the long-term effects of Mounjaro®?
The long-term effects of Mounjaro® could include inflammation of the pancreas, gallstones, and inflammation of the gallbladder. These side effects are rare.
Which is safer, Wegovy® or Mounjaro®?
Wegovy® and Mounjaro® are both safe for many people. They have similar safety profiles and can cause similar side effects. They contain different active ingredients, though. Your GP or private clinician can help you decide which medicine is best for you.
This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your GP about the risks and benefits of any treatment.