Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist licensed in the UK for type 2 diabetes and weight management. Whilst clinical trials have not established a direct link between Mounjaro and loss of libido, some patients report changes in sexual function during treatment. These changes may relate to rapid metabolic shifts, gastrointestinal side effects, psychological adjustments, or underlying health conditions rather than the medication itself. Understanding potential contributing factors and knowing when to seek medical advice can help patients manage their treatment effectively whilst maintaining overall wellbeing.

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. This dual mechanism distinguishes Mounjaro from other GLP-1 receptor agonists such as semaglutide.

The medication works by mimicking two naturally occurring hormones in the body. GLP-1 and GIP both play important roles in regulating blood sugar levels and appetite. When Mounjaro activates these receptors, it stimulates insulin secretion when blood glucose is elevated, suppresses glucagon release (which normally raises blood sugar), and slows gastric emptying. These actions help improve glycaemic control in people with type 2 diabetes.

Additionally, Mounjaro affects appetite regulation centres in the brain, leading to reduced hunger and increased feelings of fullness. This appetite suppression contributes to weight loss, which varies by dose and individual factors—clinical trials have shown weight reductions typically ranging from 5-15% in people with type 2 diabetes and higher (up to 20% at maximum doses) in people without diabetes over 72 weeks.

Mounjaro is administered once weekly via subcutaneous injection, typically in the abdomen, thigh, or upper arm. Treatment usually starts at 2.5mg weekly, with gradual dose increases as tolerated. For weight management, NHS access is restricted to specialist weight management services for patients meeting specific NICE criteria, with time-limited treatment periods.

Importantly, Mounjaro may reduce the effectiveness of oral contraceptives, particularly during treatment initiation or dose increases. Additional contraceptive methods are recommended for 4 weeks after starting treatment and after each dose increase. The medication should be avoided during pregnancy and breastfeeding, and stopped sufficiently in advance of planned pregnancy according to medical advice.

Why Might Sexual Function Change During Weight Loss Treatment?

Changes in libido or sexual function during weight loss treatment with Mounjaro can occur for several interconnected reasons, though there is no official direct link established between tirzepatide and reduced libido in the MHRA product information or clinical trials. Understanding the potential contributing factors is important for both patients and healthcare professionals.

Rapid metabolic and hormonal changes accompanying significant weight loss may temporarily affect sexual desire. Adipose (fat) tissue plays an active role in hormone production and metabolism, particularly sex hormones such as oestrogen and testosterone. As body composition changes substantially, the balance of these hormones may shift, potentially influencing libido. Additionally, the caloric deficit and nutritional changes that accompany weight loss can affect energy levels and overall vitality, which may indirectly impact sexual interest.

Gastrointestinal side effects are among the most common adverse reactions to Mounjaro, including nausea, vomiting, diarrhoea, and abdominal discomfort. These symptoms, whilst often transient, can significantly affect quality of life and general wellbeing. When someone feels physically unwell or uncomfortable, it is entirely natural for sexual desire to diminish temporarily. The medication's effect on appetite and eating patterns may also contribute to fatigue or reduced energy.

Psychological factors should not be overlooked. The process of significant weight loss, whilst generally positive, can involve complex emotional adjustments. Body image changes, relationship dynamics, stress related to lifestyle modifications, and the mental load of managing a chronic condition all potentially influence sexual wellbeing. Some individuals may experience mood changes during treatment, which can affect libido.

It is also worth noting that underlying health conditions themselves—particularly type 2 diabetes and obesity—are independently associated with sexual dysfunction. Improved metabolic health from treatment may actually enhance sexual function over time for many patients, though the initial adjustment period can be challenging. Before attributing changes to Mounjaro, it's important to consider other medications you may be taking, as many common medicines (such as certain antidepressants, blood pressure medications, or finasteride) can affect sexual function.

Managing Libido Changes While Taking Mounjaro

If you experience changes in libido whilst taking Mounjaro, several practical strategies may help, though it is important to maintain realistic expectations during the adjustment period.

Maintain balanced nutrition. Whilst Mounjaro reduces appetite, ensuring adequate nutrition remains essential. Work with your healthcare team or a registered dietitian to maintain a balanced diet with sufficient protein, healthy fats, and complex carbohydrates. Stay well-hydrated and aim for regular meals even when appetite is reduced. This supports overall energy levels and wellbeing, which can indirectly affect sexual function.

Manage gastrointestinal side effects proactively. If nausea or digestive discomfort is affecting your quality of life, discuss this with your prescriber. Eating smaller, more frequent meals, avoiding high-fat or spicy foods, and taking the injection at a time that minimises symptom impact can help. Your doctor may also adjust the dose escalation schedule if symptoms are significant.

Prioritise sleep, stress management, and physical activity. Regular exercise not only supports weight loss but can improve mood, energy levels, and body confidence—all factors that positively influence sexual wellbeing. Aim for a combination of cardiovascular exercise and resistance training in line with NHS physical activity guidelines. Adequate sleep (7–9 hours nightly) is crucial for hormonal balance and overall vitality. Stress-reduction techniques such as mindfulness, yoga, or counselling may also prove beneficial.

Communicate openly with your partner. Changes in sexual desire can affect relationships, so honest, compassionate communication is vital. Discussing your treatment, side effects, and feelings can reduce misunderstandings and maintain intimacy through non-sexual affection and connection.

Consider contraception and pregnancy planning. If you use oral contraceptives, be aware that Mounjaro may reduce their effectiveness, particularly when starting treatment or increasing doses. Additional contraceptive methods are recommended for 4 weeks after starting treatment and after each dose increase. If you're planning pregnancy, discuss this with your healthcare provider, as Mounjaro should be stopped sufficiently in advance according to medical advice.

Be patient with the adjustment period. Many side effects of Mounjaro, particularly gastrointestinal symptoms, tend to improve after the first few weeks or months of treatment. Sexual function may similarly improve as your body adjusts to the medication and as metabolic health improves.

When to Speak to Your GP About Sexual Side Effects

Whilst some fluctuation in libido during significant weight loss treatment may be expected, certain situations warrant a conversation with your GP or prescribing clinician.

Seek medical advice if:

• Changes in libido are persistent (lasting beyond 3–4 months) or severe enough to cause significant distress or relationship difficulties

• You experience other new symptoms alongside reduced libido, such as persistent fatigue, mood changes, difficulty achieving or maintaining erections (in men), vaginal dryness or pain (in women), or changes in menstrual patterns

• You have concerns about your medication or are considering stopping Mounjaro due to sexual side effects—never discontinue prescribed medication without medical guidance

• You develop symptoms of depression or anxiety, as mental health significantly impacts sexual function and requires appropriate assessment and support

• You notice signs of hormonal imbalance, such as unexpected hair loss, skin changes, or breast tenderness

• You experience menstrual irregularities or have concerns about contraceptive effectiveness while using Mounjaro

Your GP can conduct a thorough assessment, which may include reviewing your medication regimen (as other medicines can affect libido), checking relevant blood tests (including thyroid function, HbA1c, and in men with symptoms of hypogonadism, morning testosterone levels), and screening for depression or anxiety. They can also assess whether your diabetes control or other health conditions might be contributing factors.

In some cases, referral to a specialist may be appropriate—this might include endocrinology for hormonal assessment, sexual health services, or psychological support services. NICE guidance emphasises the importance of holistic care for people with diabetes and obesity, which includes addressing sexual health concerns.

Remember that sexual health is an important component of overall wellbeing, and discussing these concerns with healthcare professionals is both appropriate and important. If you believe you're experiencing side effects from Mounjaro, you or your healthcare professional can report these through the MHRA Yellow Card Scheme, which helps monitor medication safety.

Frequently Asked Questions