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Complete guide · UK
GLP-1 Medications in the UK: The Complete, Evidence-Based Guide
What GLP-1 medicines are, how they work, how Ozempic, Wegovy, Mounjaro and retatrutide actually compare, and how access works on the NHS and privately in the UK. This guide to GLP-1 medications UK covers everything currently licensed and in trials.
Contents
What are GLP-1 medications?
GLP-1 medications are a class of injectable medicines built around a hormone your gut already produces after eating.
In the UK, the two currently licensed active ingredients in this category are semaglutide (sold as Ozempic and Wegovy) and tirzepatide (sold as Mounjaro). Both are prescription-only medicines, and together they make up the entire list of GLP-1 medications UK regulators have licensed for use so far.
How GLP-1 medicines work
The mechanism comes down to three connected effects: on the pancreas, the stomach, and the brain.
- Pancreas: GLP-1 medicines increase insulin release in a glucose-dependent way, meaning the effect scales with how much sugar is actually in the blood, which lowers the risk of dangerously low blood sugar compared with older diabetes medicines. They also reduce glucagon, a hormone that raises blood sugar.
- Stomach: They slow gastric emptying, so food stays in the stomach longer. This extends the feeling of fullness after a meal.
- Brain: They act on appetite centres in the hypothalamus, reducing hunger signals and food-related cravings throughout the day.
A brief history of this drug class
The first GLP-1 receptor agonist licensed for diabetes reached patients in the mid-2000s, requiring twice-daily injections and producing modest effects on weight.
GLP-1 Medications UK: What’s Currently Available
| Medicine | Active ingredient | Receptors targeted | UK status |
|---|---|---|---|
| Ozempic® | Semaglutide | GLP-1 | Licensed — type 2 diabetes |
| Wegovy® | Semaglutide | GLP-1 | Licensed — weight management |
| Mounjaro® | Tirzepatide | GLP-1 + GIP | Licensed — diabetes and weight management |
| Retatrutide | Retatrutide | GLP-1 + GIP + glucagon | Not approved — Phase 3 trials only |
All three licensed medicines are prescription-only in the UK. This table reflects the current state of GLP-1 medications UK regulators have actually approved, rather than what’s still investigational.
Retatrutide vs Tirzepatide
Both are multi-receptor agonists, but only one is currently an approved medicine.
Mechanism of action
Tirzepatide
A dual agonist, activating GLP-1 and GIP receptors. This combination appears to produce a stronger appetite and metabolic effect than GLP-1 alone.
Retatrutide
A triple agonist, adding glucagon receptor activity on top of GLP-1 and GIP. The glucagon component is linked to increased energy expenditure, in addition to appetite reduction.
Similarities
Both are once-weekly injectable medicines built on the same underlying incretin biology. Both were developed by Eli Lilly, and both work partly through slowing digestion and reducing appetite. Gastrointestinal side effects, particularly nausea, are common to both during dose escalation — a trait shared across nearly all GLP-1 medications UK trials have studied.
Tirzepatide vs Semaglutide
Tirzepatide: 20.2% weight loss at 72 weeks
Semaglutide: 13.7% weight loss at 72 weeks
Clinical research and current evidence
Beyond weight loss itself, tirzepatide patients in SURMOUNT-5 also showed larger average improvements in several cardiometabolic markers compared with semaglutide patients.
Ozempic vs Wegovy
Same active ingredient, different licence, different purpose.
| Ozempic® | Wegovy® | |
|---|---|---|
| Active ingredient | Semaglutide | Semaglutide |
| Licensed for | Type 2 diabetes | Chronic weight management |
| Typical maximum dose | Up to 1mg or 2mg weekly | Up to 2.4mg weekly |
| UK access | Prescription, via GP or specialist | Prescription, via NHS specialist service or private prescriber |
Ozempic was approved first, for type 2 diabetes. Weight loss was observed as a secondary effect in diabetes trials.
Ozempic vs Mounjaro
| Ozempic® | Mounjaro® | |
|---|---|---|
| Active ingredient | Semaglutide | Tirzepatide |
| Mechanism | GLP-1 receptor agonist | Dual GIP/GLP-1 receptor agonist |
| Approved indications (UK) | Type 2 diabetes | Type 2 diabetes and weight management |
| Trial findings | Effective blood sugar and weight control | Generally greater average weight loss in comparative trial data |
Current research on GLP-1 therapies
This is a fast-moving field, and 2026 has already produced several notable updates.
- Retatrutide’s TRIUMPH programme has reported three Phase 3 readouts so far: TRIUMPH-4 (28.7% weight loss at 68 weeks), the pivotal TRIUMPH-1 obesity trial (28.3% at 80 weeks, up to 30.3% at 104 weeks), and TRANSCEND-T2D-1, a diabetes-specific trial showing meaningful HbA1c reduction alongside weight loss. No approval application has been filed yet.
These are prescription-only medicines
Semaglutide and tirzepatide are prescription-only in the UK and should only be used following assessment by a qualified prescriber, with an authorised product and proper ongoing monitoring. Retatrutide has no approved medical use anywhere and is not available on prescription.
This article is general information, not medical advice. If you’re considering treatment, speak to your GP or a registered UK healthcare provider about what’s suitable for you.
Frequently asked questions
What are GLP-1 medications?
They’re a class of injectable medicines that mimic the natural gut hormone GLP-1, which helps regulate appetite, digestion, and blood sugar. Semaglutide and tirzepatide are the two GLP-1 medications UK is currently licensed to prescribe.
Are GLP-1 medications available on the NHS?
Yes, but access is limited and criteria-based. Wegovy is available through NHS specialist weight management services; Mounjaro is gradually being introduced in some GP practices, subject to BMI and health criteria that vary by area.
What is the difference between Ozempic and Wegovy?
Both contain semaglutide. Ozempic is licensed for type 2 diabetes at lower maximum doses; Wegovy is licensed specifically for weight management at higher doses.
What is the difference between Ozempic and Mounjaro?
Ozempic contains semaglutide, a single GLP-1 receptor agonist. Mounjaro contains tirzepatide, a dual GIP/GLP-1 receptor agonist. Trial data suggests tirzepatide produces greater average weight loss, though individual results vary.
Is tirzepatide more effective than semaglutide?
In the SURMOUNT-5 head-to-head trial, tirzepatide produced greater average weight loss than semaglutide at 72 weeks. Side-effect profiles and tolerability differ between the two, which factors into which is right for an individual.
Is retatrutide available in the UK?
No. Retatrutide remains an investigational medicine in Phase 3 clinical trials, with no regulatory approval anywhere in the world as of mid-2026, and it is not among the licensed GLP-1 medications UK pharmacies can currently dispense.
How do GLP-1 medications cause weight loss?
They slow stomach emptying, increase feelings of fullness, and act on appetite centres in the brain, which together reduce overall food intake.
What are the common side effects?
Gastrointestinal side effects are most common: nausea, constipation, and diarrhoea, particularly during dose increases.
Can I get weight loss injections without a prescription in the UK?
No. Semaglutide and tirzepatide are prescription-only medicines and should only be used following assessment by a qualified prescriber.
What is a dual GIP/GLP-1 agonist?
A medicine that activates two hormone receptors, GIP and GLP-1, rather than one. Tirzepatide is the first licensed example of this type in the UK.
What is a triple agonist?
A medicine that activates three receptor pathways at once. Retatrutide, currently investigational, targets GLP-1, GIP, and glucagon receptors.
Do I need to stay on GLP-1 medication long-term?
Current evidence suggests weight regain is common after stopping, so these are generally considered long-term management commitments rather than short courses, something to discuss with a prescriber before starting.
Who shouldn’t take GLP-1 medications?
People with a history of pancreatitis, certain thyroid conditions, severe gastrointestinal disease, or who are pregnant are among those a prescriber will screen for before starting treatment.
How quickly do GLP-1 medications start working?
Appetite-reducing effects can be noticeable within the first few weeks, but meaningful weight loss builds gradually over months as the dose is increased under supervision. Trial results reported in this guide are measured over many months, not days.
Is weight regain guaranteed after stopping treatment?
Not guaranteed for every individual, but current evidence shows regain is common after stopping, which is why these medicines are generally considered a long-term management commitment rather than a short course, similar to how other chronic conditions are managed.
Can GLP-1 medications be combined with diet and exercise programmes?
Yes, and they’re intended to be. UK licensing and NHS pathways both expect these medicines to be used alongside dietary support and physical activity, not as a replacement for them.
Summary
GLP-1 medications have changed how obesity and type 2 diabetes are treated, moving from single-pathway drugs like semaglutide toward multi-receptor medicines like tirzepatide, with retatrutide’s triple-agonist mechanism representing the next stage still working through clinical trials.
References
- NHS England — Weight management injectionsGovernment health service
- HCPLive — Understanding SURMOUNT-5Clinical news
- TCTMD — Tirzepatide tops semaglutide for weight lossClinical news
- American College of Cardiology — SURMOUNT-5 journal scanMedical society