Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist licensed in the UK for type 2 diabetes and weight management. For people with bipolar disorder, the decision to use Mounjaro requires careful consideration of potential medication interactions, metabolic benefits, and mental health stability. Whilst bipolar disorder is not a contraindication to Mounjaro, coordinated care between your GP, psychiatrist, and mental health team is essential. This article explores the safety considerations, potential effects on mood, and practical guidance for managing Mounjaro alongside bipolar medication.

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 and, more recently, for weight management in adults with obesity or overweight with weight-related health conditions. It belongs to a class of medications known as dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonists.

The medication works by targeting two key hormone pathways involved in blood sugar regulation and appetite control. By mimicking naturally occurring incretin hormones, Mounjaro enhances insulin secretion when blood glucose levels are elevated, suppresses glucagon release (which normally raises blood sugar), and slows gastric emptying. These combined effects help to improve glycaemic control in people with type 2 diabetes.

Additionally, tirzepatide acts on areas of the brain involved in appetite regulation, leading to reduced hunger and increased feelings of fullness. This mechanism contributes to significant weight loss, which has been demonstrated in clinical trials. The medication is administered once weekly via subcutaneous injection, typically starting at 2.5 mg and gradually increasing by 2.5 mg every 4 weeks up to a maximum of 15 mg, to minimise gastrointestinal side effects.

Importantly, Mounjaro delays gastric emptying, which may affect the absorption of oral medicines, including oral contraceptives. Additional contraceptive measures are recommended for 4 weeks after starting treatment and after each dose increase. When used with insulin or sulfonylureas, there is an increased risk of hypoglycaemia, and dose adjustments of these medications may be needed.

Mounjaro is available through NHS prescription for eligible patients meeting specific criteria outlined in NICE technology appraisals for type 2 diabetes and weight management, or through private prescription. The Medicines and Healthcare products Regulatory Agency (MHRA) has approved its use in the UK, and it must be prescribed by a qualified healthcare professional as part of a comprehensive treatment plan that includes dietary modifications and increased physical activity.

Understanding Bipolar Disorder and Medication Interactions

Bipolar disorder is a serious mental health condition characterised by extreme mood swings that include emotional highs (mania or hypomania) and lows (depression). It affects approximately 1–2% of the UK population according to NHS estimates and requires long-term management, typically involving mood stabilisers, antipsychotics, or other psychiatric medications.

People living with bipolar disorder often take multiple medications to manage their condition effectively. Common treatments include lithium, valproate, lamotrigine, quetiapine, olanzapine, and other antipsychotic or anticonvulsant medications. Each of these has its own side effect profile, and many are associated with metabolic changes, including weight gain, insulin resistance, and increased cardiovascular risk.

When considering any new medication for someone with bipolar disorder, healthcare professionals must carefully evaluate potential drug interactions and the impact on both physical and mental health. Medication interactions can occur through several mechanisms: pharmacokinetic interactions (affecting how drugs are absorbed, distributed, metabolised, or excreted) and pharmacodynamic interactions (affecting how drugs work in the body).

Tirzepatide's effect on delaying gastric emptying may affect the absorption of oral medications, which is particularly relevant for people with bipolar disorder taking multiple oral medicines. For those taking lithium, there is a risk of increased lithium levels if dehydration occurs due to gastrointestinal side effects of tirzepatide, potentially leading to lithium toxicity. Additional monitoring of lithium levels may be necessary, especially during the initiation and dose escalation phases.

Weight gain is a particularly common concern for people taking psychiatric medications for bipolar disorder, with some antipsychotics causing substantial metabolic side effects. This has led to increased interest in weight management options that can be safely used alongside psychiatric treatment. However, any new medication must be carefully assessed for its potential impact on mood stability and its compatibility with existing bipolar disorder treatments. NICE guidelines on bipolar disorder emphasise the importance of monitoring physical health alongside mental health management.

Can You Take Mounjaro If You Have Bipolar Disorder?

Having bipolar disorder does not automatically exclude you from taking Mounjaro, but it does require careful consideration and close medical supervision. There is no official contraindication listed in the Summary of Product Characteristics (SmPC) for tirzepatide that specifically prohibits its use in people with bipolar disorder. However, the decision to prescribe Mounjaro must be made on an individual basis, taking into account your overall health status, current medications, and mental health stability.

Your prescribing clinician will need to conduct a thorough assessment before initiating treatment. This includes reviewing your psychiatric medication regimen, evaluating your current mood stability, and considering any history of medication-related mood changes. It is essential that your GP or prescriber is aware of your bipolar disorder diagnosis and all medications you are currently taking, including any over-the-counter supplements.

One important consideration is that many psychiatric medications used to treat bipolar disorder can cause significant weight gain and metabolic complications. In some cases, the physical health benefits of weight loss with Mounjaro may outweigh potential concerns, particularly if obesity is contributing to other health problems such as type 2 diabetes, cardiovascular disease, or sleep apnoea. NICE guidance on bipolar disorder and physical health in serious mental illness emphasises the importance of managing cardiometabolic risk factors.

If you have diabetes with pre-existing retinopathy, rapid improvement in blood glucose control with Mounjaro may temporarily worsen retinopathy, so additional monitoring may be needed. Similarly, if you have a history of pancreatitis or gallbladder disease, your doctor should consider these risks before prescribing.

For women of childbearing age, it's important to note that Mounjaro is not recommended during pregnancy, and effective contraception should be discussed. As mentioned, additional contraceptive measures are needed if using oral contraceptives.

Coordination of care between your mental health team and the prescriber of Mounjaro is crucial. If you are under the care of a psychiatrist or community mental health team, they should be informed of any plans to start weight loss medication. This collaborative approach ensures that all aspects of your health are considered and that any changes in your condition can be promptly identified and addressed. Never start or stop any medication without consulting your healthcare team.

Potential Effects of Mounjaro on Mood and Mental Health

While Mounjaro primarily targets metabolic pathways, any medication that affects weight, appetite, and eating patterns can potentially influence mood and mental wellbeing. It is important to understand that there is no official link established between tirzepatide and direct effects on bipolar disorder or mood destabilisation. The MHRA and European Medicines Agency (EMA) continue to monitor the safety profile of GLP-1 receptor agonists, with no established causal link to suicidality, though monitoring is ongoing.

The most commonly reported side effects of Mounjaro are gastrointestinal, including nausea, vomiting, diarrhoea, constipation, and reduced appetite. These symptoms, particularly if severe, can affect overall wellbeing, sleep quality, and daily functioning—factors that may indirectly influence mood stability in people with bipolar disorder. Adequate nutrition and hydration are important for maintaining mental health, so managing these side effects effectively is essential.

Weight loss itself can have complex psychological effects. For some people, successful weight loss improves self-esteem, body image, and overall quality of life, which may positively influence mental health. However, rapid or significant weight changes can occasionally trigger mood episodes in susceptible individuals. Additionally, changes in eating patterns and the relationship with food may require psychological adjustment.

Some research into GLP-1 receptor agonists has suggested potential neuroprotective effects and possible benefits for certain neuropsychiatric conditions, though this research is in early stages and not specific to bipolar disorder. Conversely, there have been rare reports of mood changes, including depression and suicidal ideation, with some GLP-1 medications, though causality has not been definitively established.

If you notice any changes in your mood, sleep patterns, anxiety levels, or experience thoughts of self-harm whilst taking Mounjaro, it is crucial to contact your GP or mental health team immediately. If you feel at immediate risk or unable to keep yourself safe, call 999 or go to your nearest A&E department. For urgent concerns, contact NHS 111 or your local crisis team. Early intervention can prevent mood episodes from escalating and ensure appropriate adjustments to your treatment plan.

If you suspect Mounjaro may be causing side effects, including any effects on your mental health, you can report this through the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk or the Yellow Card app).

Managing Weight Loss Treatment Alongside Bipolar Medication

Successfully managing Mounjaro treatment whilst taking medication for bipolar disorder requires a coordinated, holistic approach to your healthcare. Communication between all members of your healthcare team is paramount—this includes your GP, psychiatrist, mental health nurse, and any specialists involved in your diabetes or weight management care.

Regular monitoring is essential when combining these treatments. Your healthcare team should establish a monitoring schedule that includes assessment of both physical health markers (weight, blood glucose, blood pressure, lipid profile) and mental health indicators (mood stability, sleep quality, medication adherence). Keeping a mood diary or using a mood-tracking app can help you and your clinicians identify any patterns or changes that may be related to starting Mounjaro.

If you are taking lithium, be aware that dehydration from gastrointestinal side effects of Mounjaro could potentially increase lithium levels in your blood. Additional monitoring of lithium levels may be necessary, especially during the first few weeks of treatment or after dose increases. If you experience significant vomiting or diarrhoea, contact your healthcare provider promptly.

For people with diabetes who are also taking insulin or sulfonylureas, there is an increased risk of hypoglycaemia when adding Mounjaro. Your doctor may need to reduce the doses of these medications, and you should be aware of hypoglycaemia symptoms (shakiness, sweating, confusion) and how to manage them.

If you use oral contraceptives, remember that Mounjaro may reduce their effectiveness due to delayed gastric emptying. Additional contraceptive methods are recommended for 4 weeks after starting Mounjaro and after each dose increase.

Lifestyle factors play a crucial role in managing both bipolar disorder and weight. Maintaining regular sleep patterns is particularly important, as sleep disruption can trigger mood episodes. The appetite-suppressing effects of Mounjaro should not lead to skipping meals or inadequate nutrition, which can also affect mood stability. Aim for regular, balanced meals even if portion sizes are smaller. Staying well-hydrated is important, especially if experiencing gastrointestinal side effects.

Some psychiatric medications, particularly certain mood stabilisers, require regular blood tests to monitor therapeutic levels and organ function. Ensure that your prescriber is aware of all monitoring requirements and that these are maintained whilst taking Mounjaro. Weight loss may occasionally affect the distribution and metabolism of some medications, though this is not commonly reported with mood stabilisers.

Psychological support can be valuable when undertaking significant lifestyle changes. If you have access to psychological therapies through your mental health team or can access support through your GP, this may help you navigate the emotional aspects of weight loss and maintain motivation. Support groups, either for bipolar disorder or weight management, can also provide valuable peer support and practical strategies.

When to Speak to Your GP About Mounjaro and Bipolar Disorder

If you are considering Mounjaro for weight management or type 2 diabetes and have bipolar disorder, scheduling a comprehensive discussion with your GP is an essential first step. Book an appointment specifically to discuss this, rather than raising it briefly during a consultation about another matter, as your GP will need adequate time to review your medical history and current treatment regimen.

Before your appointment, prepare a list of all medications you currently take, including doses and frequency. Include any over-the-counter medications, supplements, or herbal remedies. Note any previous experiences with weight loss attempts or medications, and be prepared to discuss your current mental health stability, including any recent mood episodes or medication changes.

You should contact your GP or mental health team urgently if you experience any of the following whilst taking Mounjaro:

• Significant changes in mood (either elevated or depressed)

• Increased anxiety or agitation

• Changes in sleep patterns (insomnia or excessive sleeping)

• Thoughts of self-harm or suicide (if at immediate risk, call 999 or go to A&E)

• Severe or persistent gastrointestinal symptoms affecting your ability to eat or take medications

• Signs of dehydration

• Symptoms of hypoglycaemia if also taking insulin or sulfonylureas (shakiness, sweating, confusion)

Additionally, seek medical advice if you notice any unusual physical symptoms such as:

• Severe abdominal pain

• Persistent vomiting

• Signs of pancreatitis (severe upper abdominal pain radiating to the back)

• Symptoms of gallbladder disease (pain in the right upper abdomen, fever, jaundice)

• Symptoms of thyroid problems (lump in the neck, hoarseness, difficulty swallowing)

• Changes in vision, particularly if you have diabetic retinopathy

While rare, these require prompt medical assessment. If you suspect Mounjaro is causing side effects, report them through the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

Regular follow-up appointments should be scheduled to monitor your progress and assess both the benefits and any potential concerns. NICE technology appraisals for tirzepatide recommend regular review of treatment, and this is particularly important when managing complex conditions like bipolar disorder. Your GP can coordinate with your mental health team to ensure integrated care. If you feel that your concerns are not being adequately addressed, you have the right to request a second opinion or ask for referral to a specialist with expertise in managing metabolic health in people with serious mental illness.

Frequently Asked Questions