Weight management has become a significant focus for many adults, and medications like Mounjaro and Wegovy are increasingly part of the conversation. These drugs are designed to assist in reducing weight by targeting appetite and metabolism, offering a structured approach for individuals who struggle to lose weight through diet and exercise alone.
Understanding how these medications work, their effects, and the guidelines surrounding their use is key for anyone considering them.
How Mounjaro and Wegovy Work
Mounjaro (tirzepatide) and Wegovy (semaglutide) are administered as weekly injections using pre-filled pens that can be applied to the upper arm, thigh, or stomach. Both drugs mimic natural hormones in the body that signal fullness, effectively reducing appetite. Mounjaro additionally impacts metabolism, helping regulate energy balance more directly.
Patients typically begin with a low dose that gradually increases to a maintenance level, allowing the body to adjust and minimize side effects. This approach supports consistent weight reduction without abrupt changes to appetite or energy levels.
Expected Weight Loss
Weight loss often starts within a few weeks of treatment. Clinical trials comparing Mounjaro and Wegovy suggest that Mounjaro may lead to greater reductions. For example, in a study involving 750 participants with an average weight of 113 kg, Mounjaro users achieved an average weight loss of 20% after 72 weeks, compared to 14% with Wegovy.
However, research indicates that many people regain some weight after stopping the medication, as natural food cravings return. Ongoing support, regular check-ups, and structured diet and exercise guidance are recommended to sustain long-term results.
Eligibility for NHS Patients
Wegovy is available on the NHS in England, Wales, and Scotland for adults with a BMI of at least 35 who have weight-related conditions such as high blood pressure. Individuals with cardiovascular disease who are overweight but not obese may also qualify. Treatment is accompanied by diet and exercise programs and is prescribed for a maximum of two years.
Mounjaro has been available in specialist NHS weight-loss clinics in England and Wales since March 2025. Some GPs now offer it to patients meeting stricter criteria, including a BMI of 40 or higher (37.5 for certain minority ethnic groups) and several pre-existing conditions, such as type 2 diabetes, high blood pressure, heart disease, high cholesterol, or sleep apnea. Around 3.4 million people could eventually qualify, though nationwide rollout may take years.
Private Access and Costs
Many patients access these medications privately. Weekly pens generally cost between £100 and £300, depending on dosage. Mounjaro prices are set to increase, with the highest dose reaching approximately £247.50 per month.
It is important to avoid unregulated sources, as stricter checks have been implemented for online pharmacies to verify BMI and medical history.
Side Effects and Safety Considerations
Common side effects include nausea, vomiting, bloating, constipation, and diarrhea. Hair loss has also been reported. Most side effects are temporary, but some patients discontinue treatment due to discomfort.
Serious complications are rare but may include gallbladder or kidney issues, pancreatitis, or mood changes. The medications are most effective when combined with a structured program of diet, exercise, and medical supervision.
Pregnant or breastfeeding women should not use these medications, as their effects on unborn children are unknown. The drugs may also reduce the effectiveness of contraceptive pills, requiring alternative or additional methods of contraception.
Understanding Obesity and Healthy BMI
Obesity is defined by excess body fat, often measured using the Body Mass Index (BMI). A BMI between 30 and 39.9 is classified as obese, while a BMI of 40 or higher is considered severely obese. Different ethnic backgrounds may require lower BMI thresholds. Although BMI does not distinguish between fat and muscle, it provides a practical guideline for assessing healthy weight.
Mounjaro and Wegovy offer medically guided options for managing weight by controlling appetite and, in Mounjaro’s case, influencing metabolism. While effective for many, long-term success depends on consistent medical supervision, lifestyle changes, and regular monitoring.
Awareness of side effects, proper eligibility, and safe sourcing are essential for achieving sustainable results while maintaining overall health.