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Side effects & safety

Mounjaro side effects

The most common side effects of Mounjaro (tirzepatide) are gastrointestinal complaints such as nausea, vomiting, abdominal pain, diarrhoea and constipation. As with semaglutide, these are usually mild and occur mainly during the build-up phase. Serious side effects, such as inflammation of the pancreas, are rare. Mounjaro is prescription-only and is prescribed only by a doctor and supplied through a pharmacy; the doctor assesses whether the medicine is suitable for you. This is general information and not medical advice; consult the patient leaflet and your doctor.

Common side effects

The side effect profile of Mounjaro (tirzepatide) resembles that of semaglutide. According to the patient leaflet, the following occur commonly to very commonly:

  • Nausea and vomiting
  • Abdominal pain, diarrhoea and constipation
  • Reduced appetite and weight loss
  • Fatigue and dizziness
  • Injection site reactions

When used together with insulin or a sulfonylurea, low blood sugar (hypoglycaemia) can occur. Most gastrointestinal complaints are mild to moderate and often ease over time.

The build-up phase and side effects

Mounjaro is built up step by step. A doctor usually starts with a low dose and only increases it after a few weeks, to let the body get used to it and to limit side effects. As a result, gastrointestinal complaints occur mainly in the first weeks and shortly after each dose increase.

Never adjust the dose yourself. The titration schedule is determined by your doctor. If complaints persist, discuss this with your treating clinician.

Less common and rare, serious side effects

Sometimes (less commonly) reported are: altered taste, a tingling or numb feeling, gallstones, gallbladder inflammation and delayed gastric emptying. Serious side effects are rare:

  • Inflammation of the pancreas (pancreatitis): persistent, severe abdominal pain that may radiate to the back.
  • Severe allergic reaction (rare), such as swelling of the face, lips or throat.
For persistent severe abdominal pain or signs of an allergic reaction: contact your doctor or the out-of-hours GP service immediately.

When to make contact and reporting side effects

Contact your doctor for severe or persistent complaints, signs of dehydration from a lot of vomiting or diarrhoea, or for warning signs such as severe abdominal pain.

You can report a suspected side effect to the Netherlands Pharmacovigilance Centre Lareb via www.lareb.nl. For a complete overview of side effects, consult the patient leaflet for your product.

Frequently asked questions

Are the side effects of Mounjaro the same as those of Ozempic?
The profile is very similar: mainly gastrointestinal complaints such as nausea and diarrhoea. Tirzepatide and semaglutide are different active substances; consult the patient leaflet for each product.
Why is Mounjaro built up slowly?
By increasing the dose step by step, the body can get used to it and gastrointestinal complaints more often stay limited. The titration schedule is determined by your doctor.
When should I call my doctor while on Mounjaro?
For persistent or severe complaints, signs of dehydration, severe abdominal pain or an allergic reaction. In that case, contact your doctor or the out-of-hours GP service.

Official sources on this topic

Independent, authoritative information from official bodies:

Read more

Limiting nausea & stomach complaints→Are weight-loss medications dangerous?→About Mounjaro (tirzepatide)→Side effects of Ozempic→