Weight Loss Medication in the UK: A Patient-Centred Pillar Guide
A balanced, UK-focused overview of prescription weight loss medications—how they work, who they’re for, expected results, side effects, and how to access treatment safely.
For many people, weight management is not simply a question of willpower. Appetite, cravings, fullness, energy use, and weight regain are strongly influenced by biology—particularly hormones that signal between the gut and the brain. Prescription weight loss medication can be a helpful tool when lifestyle changes alone have not led to sustained results.
This pillar guide explains, in a clear and unbiased way, how modern medicines work, who they may be suitable for, what results to expect, and the side effects to watch for—so you can make an informed decision with your clinician.
How weight loss medications work
Many current treatments target the body’s appetite pathways. Two medicines commonly discussed in the UK are Wegovy (semaglutide) and Mounjaro (tirzepatide). Semaglutide is a GLP-1 receptor agonist, which helps you feel fuller sooner, reduces appetite, and slows stomach emptying. Tirzepatide acts on two pathways (GLP-1 and GIP), and in clinical trials has shown substantial average weight loss for many people.
It’s also helpful to know what medication does not do. These medicines are not a substitute for nutrition, movement, sleep, and stress support. Instead, they often make those changes more achievable by reducing relentless hunger and food ‘noise’.
Who may be suitable
Eligibility and best practice in the UK depends on clinical assessment, including your BMI, medical history, medications, and health risks (such as type 2 diabetes, sleep apnoea, hypertension, or fatty liver disease). A clinician should also review contraindications and whether any symptoms need investigation before starting.
Expected results and timelines
Most people notice appetite changes within the first few weeks, though meaningful weight loss typically builds over months. Dose increases are usually gradual to improve tolerability. Your clinician should monitor progress, side effects, and overall health markers—not only the number on the scale.
Side effects to be aware of
The most common side effects are gastrointestinal: nausea, reflux, constipation or diarrhoea, and reduced appetite. These usually improve over time and can often be managed with slower dose escalation, hydration, and food choices. Rare but important risks are discussed during assessment and informed consent. Seek medical advice promptly if you have severe abdominal pain, persistent vomiting, or signs of dehydration.
Access and cost in the UK
Availability can vary between NHS pathways and private providers. Costs typically depend on the medication, dose, and whether clinical follow-up is included. If you pursue private treatment, look for a regulated provider that offers proper screening, prescribing oversight, and ongoing monitoring.
What’s next: emerging medicines like retatrutide
Retatrutide is an investigational medication (not yet routinely available in the UK) that targets three hormone pathways (GLP-1, GIP, and glucagon). Early trial results are promising, but long-term safety and real-world outcomes will need to be established before it becomes a mainstream option.
How to use this pillar
This page is your hub. Use it to navigate to deeper articles on Wegovy, Mounjaro, side effect management, dose schedules, plateaus, stopping medication, and how to build a sustainable plan alongside treatment.
Further reading
• NICE guidance on obesity management and medicines
• NHS information on weight management services
• Peer-reviewed trial publications for semaglutide (STEP) and tirzepatide (SURMOUNT)