Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist licensed in the UK for type 2 diabetes and weight management. Recent concerns have emerged about whether Mounjaro causes suicidal thoughts, prompting regulatory reviews by the MHRA and EMA. Current evidence from clinical trials does not establish a causal link between tirzepatide and suicidal ideation. However, patients with obesity and diabetes have higher baseline rates of depression, and any new or worsening mood changes during treatment warrant prompt medical attention. This article examines the evidence, warning signs, and safety guidance for patients and healthcare professionals.

What Is Mounjaro and How Does It Work?

Mounjaro (tirzepatide) is a prescription medicine licensed in the UK for the treatment of type 2 diabetes mellitus and, more recently, for weight management in adults with obesity (BMI ≥30 kg/m²) or overweight (BMI ≥27 kg/m²) with weight-related comorbidities. It belongs to a novel class of medications known as dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonists. By activating both GIP and GLP-1 receptors, Mounjaro enhances insulin secretion in response to meals, suppresses glucagon release, slows gastric emptying, and reduces appetite—mechanisms that collectively improve glycaemic control and promote weight loss.

Tirzepatide is administered as a once-weekly subcutaneous injection, typically starting at a low dose (2.5 mg) and gradually titrated upwards (to 5 mg, 7.5 mg, 10 mg, 12.5 mg, or 15 mg) at approximately 4-week intervals to optimise efficacy whilst minimising gastrointestinal side effects. Clinical trials have demonstrated significant reductions in HbA1c and body weight compared with placebo and other diabetes medications. The drug's dual-agonist mechanism distinguishes it from earlier GLP-1 receptor agonists such as semaglutide (Ozempic, Wegovy) and liraglutide (Victoza, Saxenda).

Common adverse effects include nausea, vomiting, diarrhoea, constipation, abdominal pain, and decreased appetite—most of which are mild to moderate and tend to diminish over time. Serious but rare risks include pancreatitis, gallbladder disease, acute kidney injury (secondary to dehydration), and hypoglycaemia when used with insulin or sulfonylureas. If severe, persistent abdominal pain occurs (with or without vomiting), stop taking tirzepatide and seek urgent medical attention, as this could indicate pancreatitis. Patients are advised to stay well hydrated and report persistent abdominal pain or signs of dehydration promptly. The UK SmPC notes that thyroid C-cell tumours have been observed in rodent studies, though the relevance to humans remains uncertain.

Mental Health Side Effects: What the Evidence Shows

Concerns about suicidal thoughts and behaviours associated with GLP-1 receptor agonists, including Mounjaro, have emerged following post-marketing surveillance reports and patient anecdotes shared on social media. However, there is currently no established causal link between tirzepatide and suicidal ideation or self-harm based on rigorous clinical trial data. The pivotal SURPASS trials for Mounjaro did not identify a statistically significant increase in depression, suicidal thoughts, or psychiatric adverse events compared with placebo or active comparators.

In 2023-2024, the European Medicines Agency (EMA) conducted a comprehensive safety review of GLP-1 receptor agonists (including semaglutide and liraglutide) after reports of suicidal and self-injurious thoughts. The EMA's Pharmacovigilance Risk Assessment Committee (PRAC) concluded that available evidence does not support a causal association between these medicines and suicidal ideation. The Medicines and Healthcare products Regulatory Agency (MHRA) in the UK has similarly reviewed the data and continues to monitor reports closely, but has not issued specific warnings linking Mounjaro to increased suicide risk.

It is important to recognise that individuals with obesity and type 2 diabetes have higher baseline rates of depression and anxiety compared with the general population. Weight loss itself—whether achieved through medication, surgery, or lifestyle changes—can be accompanied by psychological adjustment challenges. Rapid weight reduction may alter body image, social dynamics, and self-perception, potentially unmasking or exacerbating underlying mental health conditions. Additionally, the physical effects of gastrointestinal side effects (nausea, fatigue) may contribute to mood disturbances in some patients.

Healthcare professionals should remain vigilant and enquire about mood changes during follow-up consultations, particularly in patients with a history of depression, anxiety, or previous suicidal ideation. Patients and carers should be encouraged to report any new or worsening psychological symptoms promptly.

Warning Signs and When to Seek Medical Help

Patients taking Mounjaro—and their families or carers—should be aware of warning signs that may indicate emerging mental health concerns. These include:

• Persistent low mood or sadness lasting more than two weeks

• Loss of interest in activities previously enjoyed

• Changes in sleep patterns, such as insomnia or excessive sleeping

• Feelings of hopelessness, worthlessness, or guilt

• Increased irritability or agitation

• Withdrawal from social contact or isolation

• Thoughts of self-harm or suicide, or expressing a wish to die

• Sudden changes in behaviour or personality

If any of these symptoms develop or worsen after starting Mounjaro, it is essential to contact your GP or healthcare provider without delay. Do not stop taking the medication abruptly without medical advice, as this may affect diabetes control or weight management goals. Your doctor can assess whether the symptoms are related to the medication, an underlying mental health condition, or other factors, and will work with you to adjust treatment if necessary.

In an emergency—if you or someone you know is experiencing suicidal thoughts or has harmed themselves—seek immediate help by:

• Calling 999 for emergency services

• Attending your nearest Accident & Emergency (A&E) department

• Contacting the Samaritans on 116 123 (free, 24/7 helpline)

• Reaching out to NHS 111 for urgent but non-life-threatening concerns

Early intervention and open communication with healthcare professionals are vital. Mental health support services, including talking therapies and psychiatric assessment, can be accessed through your GP or via self-referral to NHS Talking Therapies (England). Services and referral pathways may differ in Scotland, Wales and Northern Ireland. Patients with pre-existing mental health conditions should inform their prescriber before starting Mounjaro, enabling closer monitoring and coordinated care.

Safety Monitoring and MHRA Guidance for Mounjaro

The MHRA continuously monitors the safety of all medicines available in the UK, including Mounjaro, through the Yellow Card Scheme. This pharmacovigilance system collects reports of suspected adverse drug reactions from healthcare professionals, patients, and carers. Anyone who experiences a side effect—whether listed in the patient information leaflet or not—is encouraged to report it via the Yellow Card website (https://yellowcard.mhra.gov.uk) or the Yellow Card app. Reporting helps regulatory authorities detect previously unrecognised risks and take appropriate action to protect public health.

As of the latest UK Summary of Product Characteristics (SmPC), no specific warnings regarding suicidal ideation have been added to the UK SmPC or patient information leaflet for Mounjaro. As part of good clinical practice, healthcare professionals are advised to:

• Screen patients for mental health history before prescribing GLP-1 receptor agonists

• Monitor mood and psychological wellbeing during treatment, especially in the first few months

• Educate patients and carers about potential side effects and the importance of reporting new symptoms

• Consider alternative treatments in individuals with severe, unstable psychiatric illness

NICE guidance on the management of type 2 diabetes (NG28) and obesity emphasises a holistic, patient-centred approach. This includes regular review of physical and mental health, medication adherence, and quality of life. For patients prescribed weight management treatments, NICE recommends ongoing support from a multidisciplinary team, including dietitians, psychologists, and specialist nurses where appropriate.

Patients should attend all scheduled follow-up appointments and be proactive in discussing any concerns. Prescribers should document baseline mental health status and reassess this at each visit. If mental health symptoms emerge, a collaborative care plan involving the patient's GP, mental health services, and diabetes or weight management team should be established. The balance of benefits and risks must be reviewed regularly, ensuring that Mounjaro remains an appropriate and safe treatment option for each individual.

Frequently Asked Questions