Overview
Weight loss injectables are prescription medications used alongside diet and exercise to support weight management in adults living with overweight or obesity.
Use this article to:
Understand how weight loss injectables are administered
Compare the different weight loss injectables available in the UK
Check the clinical effectiveness of each option
Review eligibility criteria for treatment
What are Weight Loss Injectables?
Weight loss injectables are prescription medications designed to support weight management in adults living with overweight or obesity. These treatments are not a replacement for lifestyle changes; rather, they are intended to be used alongside a reduced-calorie diet and regular physical activity to support effective, sustainable results.
How Weight Loss Injectables Work
Weight loss injectables are taken once weekly using a pre-filled injection pen. The medication is administered subcutaneously (just under the skin), typically into any of the following areas:
Upper arm
Thigh
Abdomen
These treatments help to reduce appetite, increase feelings of fullness, and support better blood sugar regulation.
Available Weight Loss Injectables
The two main weight loss injectables available in the UK are Wegovy® and Mounjaro®. Both are highly effective when used in conjunction with consistent lifestyle support.
Wegovy® (semaglutide)
Wegovy® mimics the natural hormone GLP-1 (glucagon-like peptide-1). Clinical outcomes vary by maintenance dose:
Wegovy® 2.4 mg: Clinical studies show an average weight loss of approximately 15% of body weight over 72 weeks.
Wegovy® 7.2 mg: Clinical data from the STEP UP trial shows an average weight loss of approximately 20–21% of body weight over 72 weeks.
In addition to its proven weight management efficacy, Wegovy® is associated with additional evidence for cardiovascular benefits.
Mounjaro® (tirzepatide)
Mounjaro® is a dual-action injectable that mimics two hormones: GLP-1 and GIP. Clinical studies show an average weight loss of approximately 20–21% of starting body weight when used alongside consistent lifestyle support.
Eligibility Criteria
Weight loss injectable treatments are typically prescribed to adults (18+) who meet specific BMI (Body Mass Index) criteria:
BMI of 30 or above: With no additional weight-related conditions.
BMI of 27 or above: With specific, obesity-related health conditions, such as:
Prediabetes or Type 2 diabetes
High blood pressure (hypertension)
High cholesterol (dyslipidaemia)
Obstructive sleep apnoea
Heart disease
Treatment always starts at a low dose and is gradually increased (titration) to help the body adjust and minimise side effects.