Written by: the Medetone Medical Team
Medically reviewed by: Dr Abdullah, GPhC-registered independent prescriber
Reading time: 5 minutes · Guidance verified: October 2026
Most articles on Mounjaro contraindications list a dozen conditions together, which makes the picture more confusing than it needs to be. European labelling actually draws a clear line between three different things: the one absolute contraindication, situations where the medicine should not be used, and conditions that simply call for extra caution and closer monitoring. Understanding which is which tells you a lot more than a long undifferentiated list. Mounjaro is a prescription-only medicine and this article is informational. If you are considering treatment, the Mounjaro treatment page explains how assessment works.
At a glance
Absolute contraindication (EU): hypersensitivity to tirzepatide or any excipient
Should not be used: during pregnancy or breastfeeding
Never: alongside another GLP-1 medicine
Extra caution: pancreatitis history, gallbladder disease, severe digestive problems, diabetic retinopathy, severe liver impairment
Decided by: your prescriber, after a full history
The one absolute contraindication
Under the European product information, there is a single entry in the contraindications section: hypersensitivity to tirzepatide or to any of the excipients in the formulation.
That is it. If you have had a serious allergic reaction to tirzepatide or any ingredient, the medicine must not be used. Hypersensitivity reactions were reported in 3.2% of people on tirzepatide in placebo-controlled trials, compared with 1.7% on placebo, and were sometimes severe, including urticaria and eczema. Serious reactions such as anaphylaxis and angioedema have also been reported.
Everything else discussed below is a situation requiring caution or a reason not to use the medicine in practice, rather than a formal contraindication. Keeping that distinction clear is the most useful thing to take from any discussion of Mounjaro contraindications.
Why you may have read about thyroid cancer
This is the single biggest source of confusion, and it comes down to a difference between regulatory systems.
In the United States, the label carries a boxed warning and contraindicates the medicine in anyone with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). In European labelling, that same thyroid C-cell signal appears as a precaution rather than as a contraindication.
The underlying science is identical in both: tirzepatide caused dose-dependent thyroid C-cell tumours in rats, and it is not known whether this translates to humans, because the human relevance of the rodent finding has not been determined. The two regulators have simply taken different approaches to how it is labelled.
What this means practically: a personal or family history of MTC or MEN 2 is absolutely something to tell your prescriber, and it will weigh heavily in their decision. Our guide on how Mounjaro works explains the mechanism behind these effects.
Pregnancy and breastfeeding
Mounjaro should not be used during pregnancy or while breastfeeding. If you are planning a pregnancy, discuss timing with your prescriber well in advance.
There is a related point that catches many people out: because tirzepatide slows gastric emptying, it can affect the absorption of oral medicines, including oral contraceptives. Guidance is to switch to a non-oral contraceptive method, or add a barrier method, for four weeks after starting treatment and for four weeks after each dose increase. If you rely on the pill, raise this before your first injection rather than after.
Conditions that need extra caution
These are not absolute bars, but they change the risk calculation and require a proper clinical judgement:
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A history of pancreatitis. Acute pancreatitis has been reported with tirzepatide. If it is suspected during treatment, the medicine is stopped, and if confirmed, it is not restarted.
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Gallbladder disease. Gallbladder problems have been reported, and rapid weight loss itself raises gallstone risk.
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Severe gastrointestinal disease, including severe gastroparesis, where slowed stomach emptying can make symptoms considerably worse.
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Diabetic retinopathy, where rapid improvement in blood sugar has been associated with temporary worsening.
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Severe liver impairment, where clinical experience is limited and caution is advised.
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Taking insulin or sulfonylureas, which raises hypoglycaemia risk and may require those doses to be reduced.
One rule is firm rather than cautionary: Mounjaro must never be combined with another GLP-1 medicine. Our side effects guide covers what to watch for during treatment.
Surgery and anaesthesia
A practical point worth knowing. Because the medicine delays gastric emptying, there have been rare reports of pulmonary aspiration in people undergoing general anaesthesia or deep sedation who still had stomach contents despite fasting as instructed.
Always tell any healthcare professional that you take Mounjaro before planned surgery or any procedure requiring sedation, including dental work. This is easy to forget and genuinely matters.
Why only a clinician can decide
Reading a list of Mounjaro contraindications tells you what to raise, not whether treatment is right for you. That judgement depends on your full history, every medicine you take, and your individual circumstances, which is exactly why this is prescription-only rather than something to self-assess.
A proper consultation covers your medical and family history, current medications, previous reactions, and any planned procedures or pregnancy. You can start an assessment with a licensed clinician or read more on the Mounjaro treatment page. Patients in the UK can access treatment through Medetone UK or our partner service Rightangled, and patients in the United States through Medetone US.
Frequently asked questions
What is the only absolute contraindication in EU labelling?
Hypersensitivity to tirzepatide or any excipient. Everything else is a precaution or a practical reason not to use it.
Can I take Mounjaro with a thyroid cancer history?
Tell your prescriber. In US labelling MTC and MEN 2 history is a contraindication; in EU labelling it is a precaution that will weigh heavily in the decision.
Can I take it while pregnant?
No. It should not be used in pregnancy or while breastfeeding.
Does it affect the contraceptive pill?
It can affect absorption. Use a non-oral or additional barrier method for four weeks after starting and after each dose increase.
Can I take it with Wegovy or Ozempic?
No. Never combine Mounjaro with another GLP-1 medicine.
In summary
European labelling lists a single absolute contraindication, hypersensitivity to tirzepatide or its excipients. Beyond that, it should not be used in pregnancy or breastfeeding, never alongside another GLP-1 medicine, and with real caution where there is a history of pancreatitis, gallbladder or severe digestive disease, diabetic retinopathy, or severe liver impairment. Thyroid cancer history matters and is labelled differently in Europe and the United States. The practical takeaway is simple: disclose everything at assessment, and let a clinician weigh it.
Medical information: this article is for information only and does not replace diagnosis, prescription or medical advice. Mounjaro is a prescription-only medicine. Always disclose your full medical history and current medicines to your prescriber.
References:
AIFA, Agenzia Italiana del Farmaco (Italy): https://www.aifa.gov.it
AEMPS, Agencia Española de Medicamentos y Productos Sanitarios (Spain): https://www.aemps.gob.es
ANSM, Agence nationale de sécurité du médicament (France): https://ansm.sante.fr
CBG-MEB, College ter Beoordeling van Geneesmiddelen (Netherlands): https://www.cbg-meb.nl
BfArM, Bundesinstitut für Arzneimittel und Medizinprodukte (Germany): https://www.bfarm.de
European Medicines Agency, Mounjaro EPAR: https://www.ema.europa.eu/en/medicines/human/EPAR/mounjaro
