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Mounjaro side effects

Learn about the side effects you may experience and how best to handle them

Updated over 2 months ago

As with most prescription medications, weight loss medications can sometimes cause side effects or allergic reactions. Often, these will be mild and temporary, and will subside as your body adjusts to the treatment or the increase in dosages.

Important - if you are feeling seriously unwell please seek urgent medical assistance through your GP or nearest A&E department.


These would be for very rare symptoms such as:

  • severe allergic reaction (such as swelling of your face, lips or throat, problems breathing or swallowing or a rapid heartbeat),

  • severe pain in your stomach area (abdomen) that will not go away, with or without vomiting. You may feel the pain from your abdomen to your back.

  • pain in your upper stomach (abdomen), fever, yellowing of the skin or eyes (jaundice), or clay-coloured stools.

Common side effects, for the minority of patients that experience them, are mild and temporary and include:

  • loss of appetite

  • nausea (feeling sick)

  • vomiting (being sick)

  • dizziness

  • fatigue

  • headache

  • abdominal pain

  • acid reflux/heartburn

  • diarrhoea or constipation

  • burping and flatulence

Many of these side effects are caused by knock-on impacts rather than the medication itself. For example, vomiting or diarrhoea can lead to dehydration which presents itself as a headache and fatigue. It’s important to make sure you continue to hydrate and eat balanced regular meals throughout the day whilst taking the medication.

How to manage common symptoms

Nausea (feeling sick)

  • Eat small, frequent meals. Instead of three large meals, try eating smaller meals more frequently throughout the day.

  • Avoid greasy or spicy foods. These can aggravate nausea. Opt for bland, easy-to-digest foods like toast, rice, and bananas.

  • Stay hydrated. Drink water throughout the day, but avoid drinking large amounts at once to minimise your nausea symptoms.

Fatigue

  • Prioritise sleep. Aim for at least 8 hours of sleep per night. Create a relaxing bedtime routine and stick to a consistent sleep schedule, so that you go to bed and wake up at roughly the same time 7 days per week.

  • Stay active. Light exercise, like walking or yoga, can boost your energy levels. It’s important to try to incorporate some form of physical activity daily.

  • Healthy snacks. Keep your energy levels up by eating small, nutritious snacks like nuts, fruit, or yoghurt.

Digestive issues

  • Increase fibre. If you’re experiencing constipation, increase your fibre intake with foods like vegetables, fruits, and whole grains.

  • Stay hydrated. Drink plenty of water to help maintain a healthy digestive system and kidneys.

  • Probiotics. Consider adding probiotic-rich foods like natural yoghurt or kefir to your diet to promote healthy digestion.

Tips for staying positive

  • Celebrate small wins. Recognise and celebrate your achievements, no matter how small. This can boost your morale and keep you motivated despite your symptoms.

  • Practice gratitude. Each day, write down three things you’re grateful for. Then read them out loud to yourself. This simple practice can improve your mood.

  • Stay connected. Reach out to friends, family, or other positive social support groups to share your experiences and gain encouragement.

Nausea and vomiting tend to be the main side effects people experience when they first start treatment or move up dosages, and we can prescribe anti-sickness medication to support with this whilst your body adjusts to the treatment. Contact us and we’ll be able to advise you on the best course of action to help manage your symptoms or arrange a consult with your clinician to review your dosage and treatment plan.

The patient information leaflet received with your medication contains more information about the side effects you may experience.

An online copy is available here for easy reference.

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