What is Mounjaro?

Mounjaro (tirzepatide) is a once-weekly prescription injection used to support weight management in adults with obesity (BMI ≥ 30 kg/m²) or overweight (BMI ≥ 27 kg/m²) with at least one weight-related health condition such as hypertension, dyslipidaemia, or type 2 diabetes.

It belongs to a class of medicines called dual GIP and GLP-1 receptor agonists, which act on two natural hormones that regulate appetite, insulin, and digestion. By helping you feel full sooner, reducing hunger, and improving how your body handles blood sugar, Mounjaro can lead to clinically significant weight loss when combined with a reduced-calorie diet and increased physical activity.

What is Mounjaro Used For?

Chronic Weight Management:
Licensed in the UK to help adults with BMI ≥ 30 kg/m², or BMI ≥ 27 kg/m² with a weight-related condition, lose weight and maintain that loss alongside lifestyle measures.

Metabolic Benefits:
Weight loss achieved with Mounjaro can also help improve blood pressure, cholesterol levels and blood-sugar control.

How Mounjaro Works

Mounjaro targets two key gut-hormone receptors for a dual effect:

Enhances insulin response and lowers glucagon to steady blood glucose and curb spikes that can drive appetite.
Slows gastric emptying and boosts satiety, helping you feel fuller for longer and naturally reduce calorie intake.

When is Mounjaro Treatment Needed?

Mounjaro may be recommended if you:

Have a BMI ≥ 30, or BMI ≥ 27 with at least one weight-related comorbidity, and
Have tried a calorie-controlled diet and regular physical activity without sufficient weight loss, and
Are ready to follow a long-term lifestyle programme while under medical supervision.

Can Mounjaro Be Purchased Over the Counter?

No. In the UK, Mounjaro is a prescription-only medicine (POM). A registered prescriber must review your medical history, current medications, and treatment goals before issuing a prescription.

Alternative Treatments

If Mounjaro is not suitable, your prescriber may consider other evidence-based options such as:

Semaglutide (Wegovy): weekly GLP-1 injection for weight management.
Orlistat (Xenical/Alli): oral fat-absorption inhibitor.

Your 123Meds Prescriber will help determine the most appropriate therapy for your needs.

How to Take Mounjaro for Weight Management

Starting dose: 2.5 mg injected subcutaneously once weekly for at least 4 weeks.

Titration: Increase in 2.5 mg steps every 4 weeks as tolerated (usual maintenance 5–15 mg weekly) according to your prescriber’s plan.

Injection sites: Abdomen, thigh, or upper arm. Rotate sites each week.

Missed dose: If within 4 days, take as soon as possible; otherwise skip and continue your regular schedule.
Use only as part of a reduced-calorie diet and increased physical activity programme.

Active ingredient: Tirzepatide.

Inactive ingredients: Sodium chloride, sodium phosphate dibasic heptahydrate, sodium phosphate monobasic monohydrate, hydrochloric acid, sodium hydroxide, and water for injection.

Always read the patient information leaflet (PIL) in your pack for the complete list of ingredients, and to check for any you might be allergic to.

Most people tolerate Mounjaro well, but gastrointestinal effects are common—especially during dose increases.

Common: nausea, vomiting, diarrhoea, constipation, decreased appetite, mild abdominal discomfort.

Serious (seek urgent medical help): persistent severe abdominal pain (possible pancreatitis or gallbladder disease), signs of allergic reaction (swelling of face/lips/throat, difficulty breathing), severe dehydration, or kidney problems.

Always tell your prescriber about other medicines you take to minimise interaction risks.