NHS Issues Vital Warning on Mounjaro Use with Other Medications

The NHS has released an important notice regarding the use of the weight-loss injection, Mounjaro, particularly for patients who are also taking other medications. This advisory, published on January 4, 2026, highlights the potential interactions between Mounjaro and contraceptive methods or Hormone Replacement Therapy (HRT).

As people set new health and fitness goals for the New Year, many are considering medications that can aid in weight management. Mounjaro, known scientifically as tirzepatide, is often prescribed for those with type 2 diabetes and for adults struggling with weight loss. These medications work by slowing down gastric emptying, which can influence how effectively other drugs are absorbed in the body.

According to estimates from late 2025, hundreds of thousands of individuals in the UK are using Mounjaro to aid in weight management, with numbers possibly exceeding half a million. However, due to stringent eligibility criteria, fewer than 220,000 people are expected to receive this treatment through the NHS in the coming three years.

Key Interactions with Contraceptives and HRT

The NHS has specifically warned that for patients using the contraceptive pill, Mounjaro may reduce its effectiveness. The health service recommends that individuals consider alternative non-oral contraceptive methods, such as an implant or coil, or add a barrier method like condoms for four weeks after starting or increasing the dosage of Mounjaro.

The advisory states: “Many patients are now using weight loss medications like Tirzepatide (Mounjaro) or Semaglutide (Ozempic, Wegovy) – either for diabetes or privately for weight loss. These medications work partly by slowing down how your stomach empties, which can affect how well other medicines are absorbed by your body.”

For those using Semaglutide, the NHS indicates that while it does not appear to diminish the effectiveness of the contraceptive pill, side effects such as vomiting or diarrhoea could still impact absorption. The NHS urges patients to use additional protection in such instances.

Similarly, the notice details concerns regarding HRT. Women taking progesterone tablets, including Medroxyprogesterone acetate, may experience irregular bleeding or other complications if their HRT is affected by Mounjaro or Semaglutide. The NHS advises individuals on HRT to consult their healthcare provider to discuss options while using these weight-loss medications.

Guidance for Patients

The NHS emphasizes the importance of effective contraception when using GLP-1 agonists like Mounjaro and Semaglutide. Pregnant individuals or those planning to conceive should avoid these medications and speak with their healthcare provider immediately if they become pregnant while on them.

The notice concludes with a clear directive: “If you are considering changing your contraception, it’s recommended to discuss this with your doctor.”

As the NHS continues to provide essential information to patients navigating weight management and medication interactions, it remains critical for individuals to stay informed about the implications of combining different treatments. For further details, patients are encouraged to refer to the NHS website or contact their healthcare provider directly.