GLP-1 RAs: What They Are and the UK List (October 2026)

01 · The core answer

What is a GLP-1 RA?

GLP-1 RA is short for GLP-1 receptor agonist, the label given to a group of prescription medicines. Mounjaro (tirzepatide) is a related medicine that activates two natural gut-hormone receptors at once, GIP and GLP-1. Together these help regulate appetite, slow how quickly the stomach empties, and improve the way the body responds to insulin. In practice, most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.¹

The name is written several ways: GLP-1 RA, GLP-1RA, GLP1-RA and GLP-1 receptor agonist all mean the same thing. The plural is simply GLP-1 RAs, and you will also see GLP-1 medicines used as shorthand.

02 · The list

GLP-1 RA list: which medicines count?

These are the injectable medicines UK readers most often ask about.

Wegovy steps up after 4 weeks on each of 0.25mg, 0.5mg, 1mg and 1.7mg, so the 2.4mg maintenance dose starts from week 17.¹⁸ Liraglutide is a daily injection, unlike once-weekly Mounjaro and Wegovy. Our guide to GLP-1 dosage covers how doses are stepped up.

03 · What to do next

Is this relevant to you?

It is relevant if you are weighing up a prescription weight-management medicine. Mounjaro is licensed in the UK for weight management in adults and for type 2 diabetes, and is used alongside a reduced-calorie diet and increased physical activity.¹ The next step is a free online consultation reviewed by a GPhC-registered prescriber, who decides which medicine, if any, suits you. Our weight loss clinic explains how that works.

Related reading: Mounjaro and HRV and Rowe GLP-1.

Related guide: Mounjaro vagina.

04 · How they work

How Mounjaro works

Tirzepatide activates two natural gut-hormone receptors at once, GIP and GLP-1. Together these help regulate appetite, slow how quickly the stomach empties, and improve the way the body responds to insulin.¹

The slower stomach emptying matters in practice. With Mounjaro it can reduce how well oral contraceptive pills are absorbed. The advice is to switch to a non-oral method, or add a barrier method such as condoms, for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase. This applies to the pill only; implants, coils and injections are unaffected.¹⁷

05 · Mounjaro vs GLP-1 RAs

Where Mounjaro differs

Mounjaro is the first treatment of its kind to activate two natural gut-hormone receptors at once: GIP and GLP-1.¹ That dual action is what distinguishes it from single-action GLP-1 medicines such as semaglutide (Wegovy/Ozempic).

Many people still call Mounjaro a GLP-1 medicine, and that is a fair shorthand. The difference is that it also activates the GIP receptor.

SURMOUNT-5 is the first large head-to-head trial of tirzepatide and semaglutide for weight loss.¹⁵ Results from separate trials should not be set side by side as if they were a direct comparison.

06 · What results look like

What weight-loss results look like

No GLP-1 RA is a quick fix, and averages from trials do not predict your own result. For tirzepatide, the evidence comes from SURMOUNT-1: in the SURMOUNT-1 trial of 2,539 adults, people taking tirzepatide alongside diet and exercise lost on average 15% of their body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, compared with 3.1% with lifestyle changes alone.²

These are trial averages. Individual results vary, and treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.²

07 · Safety and downsides

Downsides and safety

The honest downsides of Mounjaro are its side effects and the possibility of regaining weight after stopping. Most side effects are digestive. The most common, affecting more than 1 in 10 people, are nausea, diarrhoea, vomiting, constipation and abdominal discomfort. Side effects are most likely when starting treatment or moving up a dose, and for most people they ease within days to a few weeks as the body adjusts.¹³

On regain, in SURMOUNT-4 people who stopped tirzepatide after 36 weeks regained on average 14% of body weight over the following year, while those who continued lost a further 5.5%.¹⁴

Serious side effects are uncommon but need urgent attention. Get medical help straight away for severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis). Get medical help straight away for pain in the upper right abdomen, fever or yellowing of the skin or eyes (possible gallbladder problems), or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing. If you take insulin or a sulfonylurea alongside Mounjaro, watch for low blood sugar (shakiness, sweating, confusion); your prescriber may need to adjust those medicines.¹³

For any new or lasting symptom, tell your prescriber and report it through the Yellow Card scheme.¹⁹ Our team provides side-effect support and ongoing monthly reviews.

Be wary of cheap lookalikes and sellers offering to supply without a consultation or prescription. You can check any pharmacy on the GPhC register; ours is GPhC 9012878.¹²

08 · Who should not take them

Who should not take Mounjaro

Mounjaro is not suitable for everyone. You should not take it if you are allergic to tirzepatide or any of its ingredients, and it should not be used during pregnancy or while trying to conceive. Mounjaro must be stopped at least one month before trying to conceive.¹³

Your prescriber will take extra care, or may recommend against treatment, if you have a history of pancreatitis, severe gut or digestive disease, diabetic retinopathy, or gallbladder problems. Always share your full medical history and medicine list during consultation.¹³

09 · NHS and private access

NHS and private access

Mounjaro is available on the NHS, but access is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the NHS primary-care rollout began in June 2025 with the highest-need groups first (initially BMI 40+ with four or more qualifying conditions).⁴⁶

Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting. NHS access to Wegovy runs through specialist weight-management services; ask your GP.