Tirzepatide is the active substance in Mounjaro. In the European Union, Mounjaro is also authorised for weight management in adults with obesity, or overweight with weight-related health problems, alongside a reduced-calorie diet and physical activity. In the United States, the same substance is marketed for weight management under the name Zepbound.
This article explains general principles; it does not determine whether treatment is indicated for you. For a comparison with semaglutide, see Wegovy vs Mounjaro.
How does tirzepatide work?
Tirzepatide activates two receptors involved in metabolic regulation: GIP and GLP-1. Through these mechanisms, it can reduce appetite, increase fullness, improve blood glucose control and support weight loss when included in a medical treatment plan.
The medicine is not a “magic injection”. Results depend on the dose, tolerability, nutrition, physical activity, sleep, other treatments and medical monitoring.
Who may be a candidate?
Weight-management treatments are generally considered for adults with obesity, or overweight plus conditions such as type 2 diabetes, high blood pressure, dyslipidaemia or sleep apnoea. The doctor assesses BMI, waist circumference, test results, any history of pancreatitis or gallbladder disease, current medicines and plans for pregnancy.
If your aim is to lose weight, start with an online nutrition consultation or the page about Mounjaro treatment.
Possible side effects
Like other incretin-based treatments, tirzepatide can cause digestive symptoms, particularly when treatment starts or the dose increases:
- nausea, a feeling of fullness or reflux;
- diarrhoea or constipation;
- vomiting or abdominal pain;
- reduced appetite, sometimes to an excessive degree.
The prescribed dose is increased gradually to reduce the likelihood of gastrointestinal reactions. Tell your doctor promptly about severe abdominal pain, persistent vomiting, signs of dehydration, symptoms of low blood glucose or any severe reaction. Dose changes must follow the doctor's instructions. Severe or persistent abdominal pain requires immediate medical advice. Difficulty breathing or swelling of the face or throat requires emergency help.
Which tests and monitoring may be useful?
Before and during treatment, the doctor may monitor weight, waist circumference, blood pressure, HbA1c, blood glucose, blood lipids, and liver and kidney function. If you have type 2 diabetes or use insulin or a sulfonylurea, the risk of hypoglycaemia needs careful discussion.
For patients with liver risk factors, assessment for metabolic fatty liver disease may be relevant, as obesity and type 2 diabetes frequently coexist with MASLD.
Tirzepatide or semaglutide?
The choice is not based only on the average percentage of weight loss in studies. Your medical profile, tolerability, other conditions, medicines, availability and long-term goals also matter. To understand the differences, read the guide to semaglutide for weight loss.
