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How long do Mounjaro side effects last?

Mounjaro (tirzepatide) is a prescription weight loss drug approved for use in the UK. Like all medicines, Mounjaro weight loss injections can cause side effects. How long these side effects will last will depend on several factors. Here, we’ll explore the common side effects, how long they might last, and the steps you can take to mitigate them.

What are the common Mounjaro side effects?

As with all medicines, Mounjaro weight loss injections can cause side effects. Some are more common than others, and many improve as your body gets used to Mounjaro. Next, we’ll explore five common side effects and what you can do to help manage them.

1. Low blood sugar (hypoglycaemia)

Mounjaro is also approved for the treatment of type 2 diabetes because it mimics incretin hormones which raise the production of insulin in the body, lowering blood glucose levels. So, it is possible that taking tirzepatide for weight loss may cause temporary hypoglycaemia.

Understand the signs of low blood sugar (hypoglycaemia), and carry a snack or drink to raise your glucose levels quickly.

Some people also report low blood pressure as a side effect of weight management therapy including Mounjaro. You should let your clinician know if you experience low blood pressure or dizziness while using Mounjaro injections because it is likely you will need monitoring.

2. Feeling sick (nausea)

Feeling sick affects between 10% and 18% of people using Mounjaro and is one of the most commonly reported side effects. Nausea can be an uncomfortable side effect, and some people share that it occurs when they increase their dose.

Nausea is more likely to occur the higher your dose of Mounjaro is, but there are ways you can manage it. For example, try drinking ginger or peppermint tea, take regular sips of water, eat smaller, more frequent meals, and distract yourself by listening to music or getting some fresh air.

3. Being sick (vomiting)

Vomiting is another common gastrointestinal effect of Mounjaro. It’s usually only mild to moderate and is most likely to occur as your dose increases and your body gets used to it.

You must stay hydrated if you are sick while using weight loss injections. Try to take small regular sips of water. You may find ginger and peppermint teas and eating small amounts of food regularly helpful.

If you are sick more than 3 times a day, this might suggest that Mounjaro is unsuitable for you. Let your clinician know if you are vomiting while using Mounjaro for weight loss.

4. Diarrhoea

Diarrhoea is experienced by 17% of people who use the 15 mg dose of Mounjaro and 13% of people on the 10 mg dose. Therefore, diarrhoea is more likely to occur if you increase your dose.

Mounjaro is associated with gastrointestinal side effects because it lowers your appetite by slowing down the time it takes for food to move through your digestive system. When it does this it can cause some discomfort, including diarrhoea, nausea, or even constipation.

If you are experiencing diarrhoea, it’s important to drink plenty of fluids to remain hydrated. You might consider rehydration salts to help balance the electrolytes you’re losing. You can also help by resting and eating small amounts of food regularly.

5. Constipation

Although the opposite of diarrhoea, more than 1 in 10 people experience constipation when using Mounjaro.

Constipation can be uncomfortable and cause other symptoms, such as discomfort or bloating. If you experience constipation, you could try:

  • Drinking plenty of water or other clear fluids such as herbal teas (ginger, peppermint, green)
  • Eating more fibre such as wholegrains, oats, fruit, vegetables
  • Taking a regular or daily walk, the movement stimulates the digestive system, encouraging food to move through the gastrointestinal tract

If you find constipation difficult, try an over-the-counter laxative to help soften and move your stools.

How long will these Mounjaro side effects last?

There isn’t a definitive answer to how long Mounjaro's side effects will last because it largely depends on how well your body tolerates the active ingredient, tirzepatide.

Like Wegovy side effects, Mounjaro side effects can last from a few days to a few weeks, but should not cause great discomfort or a prolonged reduction in quality of life.

The Mounjaro dosing schedule is titrated to reduce the risk of side effects, but some people may experience them as they increase their dose.

Frequency of Mounjaro side effects

Not everyone who uses Mounjaro for weight loss will experience side effects. Most side effects are mild and will reduce or go away on their own.

The SURMOUNT-2 study stated that 10% of participants stopped the trial because they experienced an adverse event. 87% of trial participants experienced at least one side effect. The most commonly reported side effects were nausea, diarrhoea, and constipation, which were mostly mild, and occurred as the dose increased.

Recognising serious Mounjaro side effects

Although rare, serious side effects are possible when using Mounjaro weight loss injections. It is important to recognise the signs of these adverse events, stop treatment, and seek urgent medical attention if you experience any of them.

  • Bad pain in your stomach that lasts for 6 hours or more, fever or yellowing skin. These could be signs of acute pancreatitis.
  • Extreme nausea and vomiting where you can’t keep anything down or diarrhoea that lasts for more than 2 days. This could lead to dehydration and is a medical emergency. Symptoms of dehydration include dry mouth, peeing less than normal or not at all, fast heart rate, dizziness and weakness.
  • Vision issues such as blurred vision or partial sight loss.
  • Severe stomach pain that radiates into the shoulder, fever, and vomiting. These could be signs of an infected gallbladder.
  • Any symptoms of a severe allergic reaction, such as breathing difficulties, swollen lips, tongue or throat, fast heartbeat, or trouble swallowing.


Mounjaro, like all medicines, can cause side effects but how long these will last will depend on your body’s tolerance of the active ingredient tirzepatide.

The most commonly reported side effects are those linked to the digestive system, like feeling sick, being sick, diarrhoea, or constipation. These are usually mild or moderate in severity, likely to occur as you increase your Mounjaro dose, and can often be managed at home.

Most side effects will improve with time but if you find them difficult to deal with, you should speak to your clinician for advice. They can offer you more specific advice to help you deal with the effects of Mounjaro for weight loss or discuss other weight loss options with you.

Authored By

Leanne Edermaniger

Medical Content Writer
Leanne is a science and health content writer focusing on human health and biology while utilising her solid academic background.

Published on: 21/05/2024

Reviewed By

Mohamed Imran Lakhi

MPharm - Lead Pharmacist
Imran Lakhi is the superintendent pharmacist and founder at Prescription Doctor. He has been at the core of our team.

Reviewed on: 21/05/2024
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