Like all medicines, Mounjaro can cause side effects, although not everybody gets them.

It’s normal to experience some side effects, especially when you first start treatment or increase your dose. Most patients find the side effects subside as your body adjusts to the medication. 

Managing common side effects

Nausea, diarrhoea and constipation are the most common side effects of Mounjaro. To manage these side effects, always remember to stay hydrated.

To manage nausea, consider:

• Drinking ginger or peppermint tea.
• Opting for smaller, more frequent meals throughout the day.
• Avoid very greasy or spicy foods.
• Get some fresh air if you’re feeling queasy. Take a short stroll or simply sit outside for a few minutes.

To manage diarrhoea, consider:

• Short-term use of oral rehydration solutions from a pharmacy (seek further advice from a pharmacist) or intravenous hydration from Get A Drip.
• The BRAT (bananas, rice, apple sauce, toast) diet which can help resolidify stools.
• Probiotics can help restore the balance of your gut flora. 

To manage constipation, consider:

• Adding more fibre to your diet such as fruit, vegetables and whole grains.
• Staying active (i.e. walking around more).
• If symptoms persist, short-term use over over-the-counter laxatives (seek advice from a pharmacist).

To manage bloating, consider:

• Drinking peppermint tea or taking capsules to provide some relief.
• Eating foods high in fibre can help if you are feeling constipated.
• Eating smaller, more frequent meals and chewing with your mouth closed to avoid swallowing air.
• Massaging your stomach, from right to left, to release trapped wind.
• Exercising regularly.

To manage acid reflux, consider:

• Avoiding foods that trigger your symptoms.
• Over-the-counter antacids could soothe discomfort. Speak to your local pharmacist for further advice.
• Raising your head when you lie down.
• Eat smaller meals and try not to eat 3-4 hours before bed.

To manage fatigue, consider:

• Making sure you’re consuming enough calories.
• Eat a balanced diet rich in vitamins and minerals.
• Aim for 7-8 hours of quality sleep each night.
• Engage in regular physical activity, even if it’s just light exercise such as walking or stretching.

Blood sugar monitoring

If you have diabetes, monitor your blood sugar levels closely, especially when starting or adjusting your dose, as Mounjaro can cause hypoglycemia (low blood sugar), particularly when used with other diabetes medications.

Gallstones and inflammation of the gallbladder

Gallstones are common in the general population, and many people don't even know they have them.

Mounjaro users are slightly more likely to develop gallstones and experience inflammation of the gallbladder (cholecystitis) than those who do not use this weight loss medicine.

The main reason for this is rapid weight loss of around 1.5kg (over 3 pounds) a week.

You can still use Mounjaro if you have gallstones. We’ll consider this and other factors (including your Patient Questionnaire) to assess whether Mounjaro is suitable for you.

If you develop abdominal pain, especially on the right side under your ribs, you must seek medical attention.

If you develop severe pain / vomiting / any blood in your urine or a high temperature, please call NHS 111 for advice, or attend A&E. We encourage you to continue to eat small meals throughout the day, so that weight loss doesn’t occur too quickly. Aim to stay well hydrated.

Severe and intolerable side effects

You should immediately stop taking Mounjaro if you experience any severe / intolerable side effects. If you have very severe abdominal pain which might reach through to your back, as well as nausea or vomiting: call 111 for advice, or attend A & E. Pancreatitis is a rare but serious side effect.

If you have difficulty breathing, or there is significant swelling of your face, tongue or throat, call 999 or attend A&E. You may be having a rare allergic reaction (anaphylaxis) to Mounjaro.

It’s normal for the injection site to be slightly red or pink after your Mounjaro injection; up to 1 in 10 people who use weight loss injections experience these reactions.

Some mild swelling or a small bump may also occur at the injection site. You might experience some itching too, or a mild burning sensation around the injection area.

Injection site reactions usually settle as your body gets used to the drug.

What to do: 

• Always wash your hands thoroughly with soap and water before and after administering your injection.

• Gently clean the injection site with the alcohol wipe provided (or soap and water) before and after each injection.

• If you experience any discomfort post-injection, apply a cold compress to the injection site for 10-15 minutes at a time.

• Try not to scratch or irritate the injection site, as this can worsen symptoms and increase the risk of infection. 

• If the itching or discomfort is particularly bothersome, you can take an over-the-counter non-drowsy oral antihistamine or antihistamine cream. Consult a pharmacist for further advice.

Mounjaro should be injected once weekly, on the same day each week. You can administer it at any time of the day, with or without food and drink. Keep the medication refrigerated. The pen should be disposed of 30 days after removal from fridge storage, or if the expiry date has passed.

If you miss a dose and: 

• It has been 4 days or less since you should have used Mounjaro: Use it as soon as you remember. Then inject your next dose as usual on your scheduled day.

• It has been more than 4 days since you should have used Mounjaro: Skip the issued dose. Then inject your next dose as usual on your scheduled day.

Do not use a double dose to make up for a forgotten dose. The minimum time between two doses must be at least 3 days.

If you take birth control pills by mouth, they may not work as well while you’re on weight loss medication. It’s important to talk to your GP about your birth control method while taking Mounjaro. Your GP might recommend switching to a non-oral form of contraception such as an IUD, implant or injection, which are not affected by Mounjaro.

If you continue using oral contraceptives, you should use a barrier method of contraception - especially for the first 4 weeks after starting Mounjaro or after each dose increase.

If you are planning to become pregnant, you should stop using this medicine at least 1 month in advance.

Store in a refrigerator (2°C – 8°C). Do not freeze. If the pen has been frozen, DO NOT USE. Mounjaro KwikPen can be stored unrefrigerated not above 30ºC for up to 30 days and then the pen must be discarded.