Weight Loss Injections in the UK: A Complete Patient Guide

What are weight loss injections?

Weight loss injections are prescription medicines administered by subcutaneous injection — a small needle placed just under the skin, typically in the abdomen, thigh, or upper arm. The medicines currently licensed in the UK for weight management belong to a class called GLP-1 receptor agonists. They work by mimicking a naturally occurring gut hormone called glucagon-like peptide-1, which regulates appetite, slows gastric emptying, and influences the brain's reward response to food.

The result is a significant reduction in appetite and food intake, leading to meaningful and sustained weight loss when combined with lifestyle changes.

Which weight loss injections are available in the UK?

Two injectable medicines are currently licensed in the UK specifically for weight management in adults:

• Semaglutide (Wegovy) — a once-weekly injection licensed by the MHRA for chronic weight management in adults with a BMI of 30 or above, or 27 or above with at least one weight-related health condition. Clinical trials showed an average weight loss of approximately 15% of body weight over 68 weeks.
• Tirzepatide (Mounjaro) — a once-weekly injection that acts on both GLP-1 and GIP receptors. Licensed in the UK for weight management, clinical trials showed average weight loss of up to 22.5% of body weight — the largest weight loss seen in any approved medicine to date.

Who is eligible for weight loss injections?

Eligibility is determined by a clinician based on BMI, weight-related health conditions, and medical history. Generally, adults with a BMI of 30 or above, or 27 or above with conditions such as type 2 diabetes, high blood pressure, or high cholesterol, may be eligible. A thorough medical assessment is required before any prescription is issued.

Weight loss injections are not suitable for everyone. They are not recommended during pregnancy, for people with a personal or family history of medullary thyroid cancer or multiple endocrine neoplasia type 2, or for those with a history of pancreatitis. A full medical history is taken at consultation to ensure safety.

How do you use a weight loss injection?

Both semaglutide and tirzepatide are supplied in pre-filled auto-injector pens. The injection is self-administered once a week on the same day each week. The dose is started low and increased gradually over several weeks to minimise side effects — a process called dose escalation. Most people find the injection straightforward after a brief demonstration or written instructions.

What results can you expect?

Results vary between individuals, but clinical trial data and real-world evidence consistently show meaningful weight loss. Most people begin to notice reduced appetite within the first few weeks. Significant weight loss typically becomes apparent from weeks 8 to 12 onwards. The medicines work best when combined with a reduced-calorie diet and increased physical activity.

How to access weight loss injections safely in the UK

Weight loss injections are prescription-only medicines. They must be prescribed by a registered clinician following a proper medical assessment. Purchasing them from unregulated online sources is dangerous — counterfeit products have been identified in the UK, and using prescription medicines without medical supervision carries serious health risks.

A regulated medical weight loss service will conduct a thorough assessment, issue a prescription only if appropriate, provide ongoing clinical support, and monitor for side effects throughout treatment.

Book a consultation with Weight Loss Wales to find out whether weight loss injections are right for you.