Mounjaro® side effects

Reviewed by Dr Sameer Sanghvi

What is Mounjaro®?

Mounjaro® is a new weight loss injection. If prescribed, it can be used by people with high BMIs (body mass index) to lose weight. Like with all medications, there is a chance you may experience some side effects when taking it. This article will talk through the side effects when using it to lose weight, how long they might last, and what you can do to manage them.

Potential side effects are broken down into serious, very common, common, and uncommon. We also mention the serious side effects to be aware of (uncommon and rare).

Very common side effects of Mounjaro® (may affect more than 1 in 10 people):

• Feeling sick (nausea) and being sick (vomiting)
• Diarrhoea
• Constipation  

These side effects are usually not severe and often get better over time. They can be worse when starting treatment or going up a dose. 

Common side effects of Mounjaro® (may affect up to 1 in 10 people):

• An allergic reaction – such as a rash or itching at the injection site
• Feeling dizzy
• A decreased appetite
• Stomach pain, bloating and gas
• Indigestion
• A lower blood pressure
• Heartburn or acid reflux
• Hair loss  

Uncommon side effects of Mounjaro® (may affect up to 1 in 100 people):

• Gallstones
• Pain around the injection site
• Increased calcitonin levels in the blood - picked up by your GP or a specialist 

Serious side effects of Mounjaro® (uncommon and rare):

• An inflamed pancreas (acute pancreatitis) - although uncommon, this causes serious pain in the stomach and back. It does not go away. You should get medical attention immediately if you experience this. Call 999 or go to A&E.
• Severe allergic reactions – this is rare. However, if you experience breathing difficulties, rapid swelling of the lips, tongue and/or throat, with difficulty swallowing and a faster heartbeat, you should get medical help immediately. Call 999 or go to A&E. 
• An infected gallbladder (cholecystitis) - although uncommon, symptoms include a fever, vomiting, and a severe pain in the right upper tummy moving to the shoulder. You should get medical attention immediately if you experience this. Call 999 or go to A&E.
• Changes in vision – you must tell your healthcare provider about this immediately. ​​​​​​​

Managing Mounjaro® side effects

Some of the most common side effects involve an upset stomach, feeling and being sick. The following tips will help limit the impact of these:

• Eat small and plain meals
• Get some fresh air and try and go for a walk
• Try something distracting – such as listening to your favourite music or talking to a friend on the phone
• Try food or drinks with ginger – such as ginger tea or biscuits 

Many of the side effects will get better over time as your body gets used to the weight loss treatment. However, if your side effects are bothering you, you should speak to your prescriber or your GP. They might be able to help with some advice or support or prescribe something to help you manage.

If you’ve been prescribed weight loss treatment by LloydsPharmacy Online Doctor, contact our team in your Patient Record if you’re struggling.

References

https://www.medicines.org.uk/emc/files/pil.14203.pdf
https://www.lilly.com/news/media/media-kits/mounjaro
https://www.mounjaro.com/how-to-use-mounjaro#possible-side-effects
https://www.yourhormones.info/hormones/calcitonin/
https://www.nhs.uk/conditions/acute-cholecystitis/