Can you take Mounjaro if you’ve had breast cancer?

Jump to: Understanding breast cancer remission | How Mounjaro works | Current guidelines | Practical tips | Take home message

You can take Mounjaro (tirzepatide) if you’ve been in complete remission from breast cancer for at least 6-12 months and are no longer receiving active treatment.

Still, we’d recommend letting your doctor know if you start taking Mounjaro after having breast cancer.

Breast cancer affects approximately 55,000 women in the UK annually, making it the most common cancer nationwide, representing 15% of all cancer diagnoses.

UK survival rates have improved significantly, with 85% of patients now surviving beyond five years and 76% reaching complete remission with early-stage disease.

Losing weight may help to lower the risk of recurrence in those in cancer remission.

A large meta-analysis showed that women living with obesity had a 12% higher risk of cancer recurrence than those of a healthy weight, as defined by BMI.

Plus, a randomised controlled trial showed that losing an average of 2.4kg led to a reduced risk of recurrence by 24%.

Losing weight and maintaining weight loss may help lower chronic, low-grade inflammation in the body, which can contribute to cancer cell growth.

Additionally, healthy habits essential for supporting weight loss, such as maintaining a balanced diet based on whole foods and getting sufficient sleep, will naturally enhance our overall health and reduce our risk of cancer recurrence.

Mounjaro may indirectly support a reduced risk of cancer recurrence by promoting weight loss, providing an opportunity to develop healthy habits in the long term.

Most breast cancer survivors will likely respond similarly to Mounjaro as the general population, achieving 20-26% total body weight loss within 12 months.

You should not take Mounjaro if you have:

• Current active cancer or ongoing cancer treatment
• Family history of thyroid cancer or multiple endocrine neoplasia syndrome type 2 (MEN 2)
• Current diagnosis of thyroid cancer
• An eating disorder, such as anorexia or bulimia

Before starting Mounjaro after breast cancer:

1. While not essential, it’s recommended to wait 6-12 months after completing treatment
2. Schedule a medication review covering all current medicines and supplements
3. Continue all recommended cancer follow-up appointments and mammograms

Let’s examine the relationship between breast cancer remission and Mounjaro in greater detail.

Understanding breast cancer remission

Breast cancer remission indicates the reduction or disappearance of cancer following treatment.

NHS oncologists recognise several distinct remission categories:

Complete remission means no detectable cancer remains after treatment. UK physicians often document this as “no evidence of disease” (NED) in medical records.

Partial remission occurs when tumours shrink by at least 30% but remain detectable on imaging.

Stable disease refers to cancer that has not grown or shrunk significantly (i.e., less than a 20% change in either direction).

Progressive disease indicates cancer growth of 20% or more, or new tumour sites.

For Mounjaro eligibility, complete remission is required.

UK data shows 76% of breast cancer patients achieve complete remission, with rates reaching 90% for stage 1 disease diagnosed through NHS screening programmes.

Many clinicians may recommend a waiting period of 6-12 months after completing cancer treatment before starting any weight management medications.

This recovery period serves two purposes: it allows treatment-related inflammation to resolve, which typically takes 3-6 months, and confirms stable remission, requiring at least two clear follow-up assessments.

NHS oncologists confirm remission status through:

• Physical examinations every 3-6 months during the first two years
• Blood tests measuring tumour markers like CA 15-3 (though not routinely used in all cases)
• Annual mammograms on the affected and unaffected breasts
• Ultrasound or MRI studies for high-risk patients or when symptoms warrant

Many breast cancer survivors continue preventative treatments while in remission.

Around 70-80% of UK patients with hormone-receptor-positive breast cancer take hormone therapy (tamoxifen or aromatase inhibitors) for 5-10 years.

These ongoing hormonal treatments don’t affect Mounjaro eligibility. In fact, weight loss may improve outcomes for women on these medications by reducing side effects and potentially enhancing efficacy.

How Mounjaro works

Mounjaro (tirzepatide) is a dual-action weight-loss injection that works by lowering hunger and reducing the rewarding effects of food.

The medication mimics two hormones – GLP-1 and GIP – that your body naturally produces in response to eating.

These hormones regulate appetite through multiple mechanisms:

1. They slow gastric emptying by 30-40%, keeping food in your stomach longer so you feel fuller for longer.
2. They directly signal your brain’s hypothalamus (appetite control centre), reducing hunger sensations and food cravings.
3. They improve insulin sensitivity by 20-30%, helping your body process blood sugar more efficiently and reducing the blood glucose spikes that can trigger hunger.

Research published in JAMA in 2024 indicates that Mounjaro results in an average weight loss of 26% after 72 weeks of treatment.

Research shows 9 out of 10 users lose at least 15% of their starting weight, with individual results varying based on starting BMI, diet, physical activity, and medical history.

Mounjaro offers additional benefits, particularly relevant for breast cancer survivors:

Reduced inflammation: The medication lowers inflammatory markers, such as C-reactive protein, addressing the chronic inflammation associated with both cancer risk and recurrence.

Improved cardiovascular health: Mounjaro reduces blood pressure by an average of 8-10 mmHg systolic, which is important after treatments like anthracycline chemotherapy that may affect heart function.

Improved fat distribution: The medication reduces visceral fat (the dangerous fat around organs) by up to 40%, more than subcutaneous fat, potentially reducing cancer-promoting hormones produced by this tissue.

Current guidelines

UK medical authorities have established clear guidelines regarding Mounjaro eligibility for cancer patients and survivors:

You can’t take Mounjaro if you have:

• A current cancer diagnosis requiring treatment
• A personal or family history of medullary thyroid carcinoma (MTC)
• Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)
• A current thyroid cancer diagnosis

You can take Mounjaro if:

• You’ve completed all breast cancer treatments (surgery, chemotherapy, radiation)
• Your NHS oncologist has documented complete remission in your medical records
• A minimum of 6 months has passed since your last active treatment (12 months recommended)
• You meet standard eligibility criteria (BMI ≥30 or ≥27 with weight-related conditions)
• Your most recent follow-up scans and blood tests show no evidence of disease

The Medicines and Healthcare products Regulatory Agency (MHRA) has not identified any specific contraindications for GLP-1 medications in cancer survivors who meet these criteria.

The National Institute for Health and Care Excellence (NICE) acknowledges that clinical trials for Mounjaro excluded patients with a recent history of cancer.

However, their current guidance permits use in cancer survivors in complete remission based on:

1. The medication’s known mechanisms of action
2. The absence of biological pathways that would increase cancer risk
3. The potential benefits of weight management for cancer survivors

Practical tips

1. Keep in touch with your healthcare team

Maintaining open communication with your medical providers is crucial.

We recommend informing your GP and oncologist that you’re starting Mounjaro.

Second Nature’s monthly check-in forms, reviewed by our clinical team, provide an additional layer of safety monitoring throughout your treatment.

These regular assessments help identify any concerns early, ensuring your medication experience remains safe, positive, and effective.

2. Eat a diet based on whole foods

Nourishing your body with nutrient-dense foods becomes especially important when taking Mounjaro after breast cancer treatment.

Second Nature’s balanced plate model offers a foundation to build a healthy diet on:

• Fill half your plate with a variety of non-starchy vegetables to provide essential vitamins, minerals, fibre, and plant compounds that support overall health.
• Dedicate a quarter of your plate to quality protein sources – like poultry, fish, eggs, red meat, tofu, or legumes – which become especially crucial during weight loss to preserve precious muscle mass.
• The remaining quarter accommodates complex carbohydrates such as brown rice, sweet potatoes, or whole grains, providing sustained energy without blood sugar spikes.
• Include a tablespoon of healthy fats – olive oil, avocado, or nuts – which help your body absorb essential nutrients like vitamin D and K.

This balanced approach ensures you’re nourishing your body and mind to support long-term health and weight loss.

3. Exercise regularly

Movement and exercise significantly improve our health, no matter the number on the scales.

If you’re new to exercise, consider starting gently with walking or swimming, and gradually build to include resistance training 2-3 times a week.

These strength exercises are particularly valuable during weight loss, as they help maintain muscle that increases our energy expenditure and reduces the risk of falls as we age.

Short bursts of exercise, known as ‘exercise snacks,’ can also be highly beneficial. This could be doing 5 press-ups while waiting for the kettle to boil, or doing calf raises while you’re cooking.

Take home message

Breast cancer survivors in complete remission can safely take Mounjaro, with research suggesting weight management may reduce recurrence risk by around 24%.

Additionally, the healthy habits that support long-term weight loss will also improve our overall health and reduce the risk of cancer recurrence by lowering chronic, low-grade inflammation and hormones like insulin, which can promote cancer cell growth.

Second Nature’s medication programme

Second Nature provides Mounjaro as part of our Mounjaro weight-loss programme.

Why should you choose Second Nature over other providers, assuming you’re eligible?

For peace of mind.

Second Nature has worked with the NHS for over 6 years, providing weight-loss programmes across the UK.

While our Mounjaro weight-loss programme is private and not currently used by the NHS, we’ve built the programme focusing on scientific evidence, patient safety, and data security.

We hope that our 6+ years of working with the NHS and building a track record of effective weight-loss results will give you peace of mind to give us a try.