Ozempic®, Wegovy® and Mounjaro®: differences in diabetes and weight management

Three medicines, two different active ingredients

Ozempic® and Wegovy® contain semaglutide. Mounjaro® contains tirzepatide.

Semaglutide acts on GLP-1 receptors, which are involved in regulating blood glucose and appetite. Tirzepatide acts on two types of receptors: GLP-1 and GIP.

These medicines are not insulin. They help the pancreas release insulin when blood glucose rises, among other effects. The injectable forms discussed here are administered once a week.

Ozempic®: a treatment for type 2 diabetes

Ozempic® is indicated for adults whose type 2 diabetes is insufficiently controlled, alongside diet and physical activity.

It can be combined with other diabetes medicines or used alone when metformin is unsuitable because of intolerance or a contraindication.

Its purpose is to improve blood glucose control. Weight loss may also occur, but Ozempic® is not licensed specifically for weight management.

It is therefore important to distinguish a possible effect of the medicine, such as weight loss, from the indication for which it is prescribed.

Wegovy®: a treatment for weight management

Wegovy® contains semaglutide, like Ozempic®, but its weight-management indication is different.

For weight management in adults, its UK licence allows use alongside a reduced-calorie diet and increased physical activity in people with:

• A BMI of 30 kg/m² or higher;
• A BMI of at least 27 but below 30 kg/m², with at least one weight-related health condition.

Type 2 diabetes can be one of these associated conditions. Someone with diabetes may therefore receive Wegovy® as part of weight-management care if they meet the criteria. This does not make it a medicine specifically licensed to treat type 2 diabetes.

Wegovy® also has a UK indication for reducing major cardiovascular events in certain adults with established cardiovascular disease and overweight or obesity.

Doses and prescribing instructions differ from those for Ozempic®. Sharing an active ingredient does not mean that you can switch products yourself.

Mounjaro®: a dual action and two treatment purposes

Mounjaro® acts on both GIP and GLP-1 receptors. This dual action contributes to blood glucose control and reduced appetite.

In the UK, it is licensed for insufficiently controlled type 2 diabetes. It is also licensed for weight management in eligible adults with obesity, or overweight with at least one weight-related health condition.

For adult weight management, the BMI criteria are:

• A BMI of 30 kg/m² or higher;
• A BMI of at least 27 but below 30 kg/m², with at least one weight-related health condition.

These indications address different treatment goals, although both may apply to the same person.

The main differences to understand

The first difference is the active ingredient: Ozempic® and Wegovy® contain semaglutide, while Mounjaro® contains tirzepatide.

The second is how they work. Semaglutide targets GLP-1 receptors, whereas tirzepatide targets both GLP-1 and GIP receptors.

The third is their licensed use. Ozempic® treats type 2 diabetes. Wegovy® is used for weight management, while Mounjaro® is licensed for both purposes in eligible patients.

Finally, a medicine’s licence and NHS prescribing criteria are not the same. Meeting the licensed criteria does not automatically mean that treatment is available through the NHS. Access depends on the relevant recommendations and local care arrangements.

What side effects and precautions should you know about?

The most common side effects involve digestion: nausea, diarrhoea, vomiting and, depending on the medicine, constipation or abdominal pain. These may occur particularly when treatment begins or the dose increases.

The risk of low blood glucose, or hypoglycaemia, needs particular attention when one of these treatments is combined with insulin or a sulfonylurea. The doctor may need to adjust the accompanying medicine.

Severe, persistent abdominal pain requires urgent medical advice, including assessment for pancreatitis. Repeated vomiting can also lead to dehydration.

Pregnancy plans and contraception should be discussed with the prescriber. These medicines should not be used during pregnancy. People taking Mounjaro® who use an oral contraceptive should discuss additional barrier contraception or a non-oral method for four weeks after starting treatment and for four weeks after each dose increase.

Tell your doctor or pharmacist about any troublesome or persistent side effects so they can advise you on what to do.

Choosing treatment means considering your whole situation

Choosing a treatment involves more than comparing its effect on weight.

For type 2 diabetes, the doctor considers blood glucose control, current medicines, other health conditions, tolerability and the goals agreed with the patient. Follow-up appointments help assess both benefits and difficulties.

Weight loss alone does not show whether diabetes is well controlled. Blood glucose readings and HbA1c remain important measures.

Nutrition, appropriate physical activity and ongoing support are also part of care. If injections, digestive side effects or treatment demands become difficult to manage, discuss them with your care team rather than changing doses or stopping treatment yourself.

The aim is to find a treatment that is effective, manageable and suited to daily life.

Key takeaways

Ozempic® treats type 2 diabetes, Wegovy® is used for weight management, and Mounjaro® is licensed for both purposes in eligible patients in the UK.

Even when medicines share an ingredient or have similar effects, they are not interchangeable without a medical decision. Prescribing and treatment changes require an individual assessment.

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