Mounjaro vs Wegovy: what is the difference?

How They Work

Wegovy contains the active ingredient semaglutide, which belongs to a group of medicines called GLP-1 receptor agonists. It works by acting like a natural hormone in the body known as GLP-1 (glucagon-like peptide-1. This hormone helps regulate appetite and food intake, slows the emptying of the stomach, and signals to the brain that you feel full.

Mounjaro contains the active ingredient tirzepatide. It acts on two naturally occurring hormones involved in appetite and blood sugar regulation: GLP-1 and glucose-dependent insulinotropic polypeptide (GIP). Like GLP-1, GIP is involved in regulating insulin release and appetite. By acting on both pathways, Mounjaro influences feelings of fullness, food intake, and blood sugar levels.

Both medicines are given as a once-weekly injection under the skin. They affect hormones that play a role in hunger and digestion, which is why they are used as part of an overall weight management plan alongside healthy eating and regular physical activity.

Although the way they work are similar in some respects, they are different molecules and are not interchangeable. A healthcare provider will consider individual health factors when deciding which medicine may be the right one for you.

Approved Uses for Mounjaro and Wegovy in New Zealand

Wegovy is approved in New Zealand for weight loss and weight maintenance, alongside diet and physical activity, in adults with a BMI of 30 kg/m² or higher, or 27 kg/m² to under 30 kg/m² if they also have weight-related health conditions. It is also approved to reduce the risk of heart-related events in adults with a history of heart disease who have a BMI of 27 kg/m² or higher. In adolescents aged 12 years and over, Wegovy may be used for weight management in those with obesity and a body weight above 60 kg.

Mounjaro is approved in New Zealand for weight management, including weight loss and weight maintenance, in adults who are overweight or have obesity. It is also approved to improve blood sugar blood sugar levels in adults with type 2 diabetes. It may be used on its own or together with other diabetes medicines. Unlike Wegovy, Mounjaro is not approved for use in adolescents.

Both medicines are intended to be used alongside dietary changes and increased physical activity. A healthcare provider will assess whether a person meets the criteria for treatment and whether the medicine is appropriate based on their overall health.

Dosing Differences

Wegovy is taken as a once-weekly injection under the skin. Treatment begins at a low dose of 0.25 mg once weekly. The dose is increased in stages every four weeks over about 16 weeks until the usual maintenance dose of 2.4 mg once weekly is reached. Once at the maintenance dose, it is not increased further. The gradual increase is designed to help reduce gastrointestinal side effects while the body adjusts.

Mounjaro is also taken as a once-weekly injection under the skin. Treatment begins at 2.5 mg once a week for the first four weeks. After this, the dose is increased to 5 mg once weekly. If needed, the dose may then be increased in 2.5 mg steps every four weeks to 7.5 mg, 10 mg, 12.5 mg, or up to a maximum of 15 mg once weekly. Not everyone will require the higher doses, and the appropriate dose is determined by a healthcare provider.

Wegovy is intended to be used once weekly, ideally on the same day each week. If needed, the injection day can be changed, provided there has been sufficient time since the previous dose.

Mounjaro is also used once weekly, preferably on the same day each week. If a change of day is required, there should be an appropriate interval between doses. Your healthcare provider will advise you on how to do this safely.

Please note: Mounjaro and Wegovy are different prescription medicines and are not intended to be used at the same time. A healthcare provider will determine which single treatment is appropriate based on your individual circumstances.

Side Effects of Wegovy and Mounjaro

Because Wegovy and Mounjaro affect similar appetite and digestive pathways, they share many of the same types of side effects. The most common side effects with both medicines affect the stomach and digestion. These can include nausea, vomiting, diarrhoea, constipation, and stomach discomfort. They are more likely to happen when treatment first begins or when the dose is increased

Both medicines can also cause low blood sugar when used with certain other diabetes medicines, and both carry warnings about more serious but less common risks such as inflammation of the pancreas, gallbladder problems, allergic reactions, and bowel obstruction.

The likelihood and severity of side effects can vary from person to person. For a detailed breakdown of common and serious side effects, see:

If you experience symptoms that are severe, persistent, or concerning, speak with your healthcare provider.

• Mounjaro Side Effects: What You Should Know
• Wegovy Side Effects: A Complete Guide

Access and Availability in New Zealand

Mounjaro and Wegovy are both prescription medicines in New Zealand. They are not available over the counter and must be prescribed by a healthcare provider after a consultation and medical assessment.

At present, neither Mounjaro nor Wegovy is publicly funded in New Zealand. This means you will need to pay for the medicine. You may also be required to pay for any consultations with your healthcare provider. Costs can vary between pharmacies, and ongoing treatment will involve continued prescription and follow-up appointments.

Which One Might Be Considered?

There is no single medicine that is right for everyone. The choice between Wegovy and Mounjaro depends on individual health factors, treatment goals, and medical history.

Wegovy is approved specifically for weight loss and weight maintenance, and in certain adults with established heart disease, to reduce the risk of heart-related events. It may be considered for people who meet the BMI criteria for treatment and who are looking for a medicine approved solely for weight management.

Mounjaro is approved for weight management in adults who are overweight or have obesity, and it is also approved to improve blood sugar control in adults with type 2 diabetes. For individuals who have type 2 diabetes as well as overweight or obesity, a healthcare provider may consider these factors when discussing treatment options.

Dosing schedules, side effect profiles, personal tolerance, existing medical conditions, and overall treatment plans may also influence the decision. Cost and availability are practical considerations, particularly as neither medicine is publicly funded in New Zealand.

These medicines are not interchangeable and are not intended to be used together. A healthcare provider will assess eligibility, discuss potential risks and benefits, and recommend a single treatment based on individual circumstances.

If you are unsure which option may be appropriate, the safest approach is to have a detailed discussion with your healthcare provider, who can guide you based on your health history and current needs.

Important safety information

Prescription medicine. Mounjaro® (tirzepatide) is used in adults with type 2 diabetes to improve blood sugar control. In adults who are overweight or have obesity, Mounjaro® is also used for weight management, including weight loss and weight maintenance. Mounjaro® contains the active ingredient tirzepatide and is available in prefilled KwikPen® devices in strengths of 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg and 15 mg. Mounjaro® has risks and benefits. Ask your healthcare provider if Mounjaro® is right for you. Use strictly as directed. If you experience side effects, see your healthcare provider. For more information, refer to the Mounjaro® Consumer Medicine Information (CMI) available at: https://www.medsafe.govt.nz/Consumers/cmi/m/Mounjaro.pdf

Prescription medicine. Wegovy® (semaglutide) is used for weight loss and weight maintenance, in addition to diet and physical activity, in adults with a BMI of 30 kg/m² or greater (obesity), or 27 kg/m² to less than 30 kg/m² (overweight) with weight-related health problems. Wegovy® is also used to reduce the risk of a heart disease–related event in adults with a history of heart disease who have a BMI of 27 kg/m² or greater. In adolescents aged 12 years and above, Wegovy® is used for weight management in those who have obesity and a body weight above 60 kg. Wegovy® contains the active ingredient semaglutide and is available as a prefilled pen in strengths of 0.25 mg, 0.5 mg, 1 mg, 1.7 mg and 2.4 mg. Wegovy® has risks and benefits. Ask your healthcare provider if Wegovy® is right for you. Use strictly as directed. If you experience side effects, see your healthcare provider. For more information, refer to the Wegovy® Consumer Medicine Information (CMI) available at: https://www.medsafe.govt.nz/consumers/cmi/w/wegovy.pdf