Is Mounjaro Safe? What You Need to Know

Mounjaro is an injectable treatment for weight loss that contains the active ingredient tirzepatide.

Mounjaro supports weight loss by mimicking hormones produced by the body to control appetite, slow the emptying of the stomach and reduce food cravings. The medication is injected once per week and should be taken alongside a lower-calorie diet and regular exercise.

Mounjaro is a dual agonist, meaning it targets two sets of hormones in the body: glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) to aid weight loss. Mounjaro has undergone extensive clinical studies that involved thousands of participants and was approved as a safe treatment for weight loss. However, as with all medications, there is a risk of experiencing side effects and adverse reactions. Therefore, our experts have compiled this guide with key precautions and considerations to be aware of before taking Mounjaro, to help you make an informed decision about whether the treatment is right for you.

Is Mounjaro safe?

Mounjaro was recently approved by the Medicines and Healthcare products Regulatory Agency (MHRA) as a safe and effective treatment for weight loss after undergoing a series of clinical trials.

Like all medications, Mounjaro may cause side effects, which patients should be aware of and understand how to manage. If you suffer from certain health conditions or are currently taking some medications, you are more at risk of adverse responses to Mounjaro.

Our pharmacists have prepared this overview of the medication to keep you informed, whether you are looking to start your weight loss journey or continue your course of treatment with Mounjaro.

In order to make sure you administer the medication safely and effectively, read our guide on How to Take Mounjaro Injections.

Is Mounjaro available over the counter?

No, Mounjaro is a prescription-only medication, as your body’s response to the medication needs to be monitored carefully throughout the course of your treatment.

When Mounjaro is prescribed, your medical history will be considered, including any previous and current health conditions, medications and your body mass index (BMI). Your BMI must be 30 kg/m² or over (obese), unless you have a weight-related health condition such as high cholesterol, high blood pressure, pre-diabetes or other serious conditions, in which case your BMI must be between 27 and 30 kg/m² (overweight).

Taking Mounjaro without a prescription is not safe. Like all medications, it carries a small risk of side effects, some of which can be serious. While most side effects are mild and often improve over time, it is important to be aware of them and report any symptoms to your prescriber. This helps ensure your safety and allows your treatment to be adjusted if needed.

The Mounjaro dosage schedule is carefully designed to gradually introduce tirzepatide, the active ingredient, into your system in order to help reduce the likelihood and severity of side effects.

Managing Mounjaro side effects

Common side effects

The most frequently reported side effects with Mounjaro are usually mild to moderate in severity and occur when treatment is started or the dose is increased. They consist of:

• Nausea
• Diarrhoea
• Vomiting
• Constipation
• Stomach (abdominal) pain
• Indigestion (dyspepsia)

These gastrointestinal side effects are primarily caused by Mounjaro's effect on slowing gastric emptying and its interaction with gut hormones.

It is important to be aware that diarrhoea or vomiting can lead to dehydration, which may be serious. Make sure to stay hydrated during your treatment and contact your GP or doctor if you experience these symptoms.

Serious side effects

While less common, it is important to be aware of the more serious potential side effects associated with Mounjaro. If you experience any of the following, you should immediately seek medical attention.

• Pancreatitis: This is an acute inflammation of the pancreas, which can be a serious and potentially life-threatening condition. Symptoms include severe, persistent pain in the upper abdomen that may radiate to your back, often accompanied by nausea and vomiting.
• Gallbladder problems: This can include gallstones (cholelithiasis) or inflammation of the gallbladder (cholecystitis). Symptoms may include sharp pain in the upper right abdomen, fever, jaundice (yellowing of your skin or eyes) and clay-coloured stools.
• Serious allergic reactions (hypersensitivity): Though rare, severe allergic reactions are possible. Signs include swelling of your face, lips, tongue, or throat (angioedema), difficulty breathing or swallowing, a severe rash or itching, dizziness or fainting, and a rapid heartbeat. Seek immediate medical attention and inform your doctor straight away if you experience any of the symptoms above.
• Hypoglycaemia (low blood sugar): The risk of low blood sugar is generally low when Mounjaro is used alone. However, this risk significantly increases if Mounjaro is taken in combination with other medications that lower blood sugar, such as insulin or sulfonylureas. Symptoms of hypoglycaemia include dizziness, shakiness, sweating, confusion, irritability, headache, and rapid heart rate.

Who should not take Mounjaro?

Mounjaro is not suitable for everyone. Generally, Mounjaro is contraindicated or should be used with caution in individuals with:

• A personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)
• A known hypersensitivity or allergic reaction to tirzepatide or any of Mounjaro's excipients
• Pregnancy and breastfeeding
• A prior history of pancreatitis
• Severe impairment of kidney or liver function
• Severe gastrointestinal disease, such as significantly slowed stomach emptying (gastroparesis), which can be exacerbated by Mounjaro's effects on gastric motility. Patients with severe inflammatory bowel disease or other severe gastrointestinal issues may not be suitable
• Type 1 diabetes
• Retinopathy
• Alcohol use disorder (alcoholism)
• Acromegaly or any growth hormone problem
• Addison's disease
• Congenital adrenal hyperplasia
• Cushing's syndrome
• Heart disease (e.g. ischaemic heart disease, heart attack, heart failure, irregular heartbeat, cardiomyopathy)
• Hypoglycaemia
• Depression and/or any other mental illness
• Any form of cancer
• Any serious medical condition which may require immediate hospitalisation
• An eating disorder such as anorexia nervosa or bulimia

Conclusion

Mounjaro is a safe medication and is approved by the Medicines and Healthcare products Regulatory Agency (MHRA). However, understanding the potential side effects, contraindications, and drug interactions is important to make an informed decision about the treatment. You should take Mounjaro according to its prescribed schedule - for more information, read our Mounjaro Dosage Guide.

At Pharmica, we offer a free online consultation to assess your eligibility for treatment, along with ongoing support from our clinical team to help you achieve safe, effective, and sustainable weight loss.

Ready to start your weight loss journey?

Pharmica is the #1 Weight Loss Service in the UK on Trustpilot and offers Mounjaro alongside other clinically-proven weight loss treatments. Our qualified healthcare professionals provide comprehensive consultations to determine if Mounjaro is right for you, ensuring safe and effective treatment tailored to your individual needs.

Sources

• Medicines and Healthcare products Regulatory Agency (MHRA). Mounjaro (tirzepatide) Public Assessment Report. [Accessed 25th July 2025]
• NHS England. Tirzepatide (Mounjaro®) for the management of obesity. [Accessed 25th July 2025]
• Mayo Clinic. Tirzepatide (Subcutaneous Route) - Side Effects. [Accessed 25th July 2025]