GLP-1 Injectable Treatments in the UK (October 2026)

01 · The core answer

What is a GLP-1 injectable?

It is a medicine that activates the GLP-1 hormone pathway to help regulate appetite, using a pre-filled pen you inject under the skin.

Tirzepatide, the medicine in Mounjaro, 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 how the body responds to insulin.¹ Most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.

02 · Your decision

Is an injectable right for you, and what next?

The first decision is injection versus tablet. Mounjaro and Wegovy are once-weekly injections, while Wegovy tablets and Foundayo are once-daily tablets; a prescriber will check which option is suitable for your health, your other medicines and your routine. Compare them in our oral versus injectable comparison, or see the non-injectable options.

The second decision is where to be treated. If you want to start privately, our weight loss clinic explains the process, and a GPhC-registered prescriber reviews every consultation. Your first 2.5mg Mounjaro pen costs £129.99 with code FIRST40 (standard price £169.99).

Related guide: Are all glp 1 injectable.

03 · UK injectable options

Which injectable GLP-1 medicines are available in the UK?

Mounjaro is a once-weekly injectable made by Eli Lilly, licensed in the UK for weight management in adults and for type 2 diabetes. It comes as a multi-dose KwikPen.¹ Wegovy is semaglutide, also once weekly, and steps up after at least four weeks, reaching the 2.4mg maintenance dose from week 17.¹⁸ Our Wegovy pen page lists current options.

Liraglutide is a daily injection, unlike once-weekly Mounjaro and Wegovy. Not every GLP-1 medicine is an injection, as this explainer on whether GLP-1 is only injectable shows.

04 · Does it work?

Does a GLP-1 injection really work?

Yes, in trials tirzepatide produced substantial average weight loss. 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. These are trial averages — individual results vary, and treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.²

For a deeper look at outcomes, read our page on injectable GLP-1 weight loss treatment.

05 · Pace and first weeks

How long does a GLP-1 injection take to kick in?

Some people notice appetite change and early loss in week one, others feel little until a higher dose — both are normal. Early loss includes water weight, so the trend over weeks matters more than any single weigh-in.¹ Weight loss is gradual by design: the first weeks on 2.5mg are an adjustment phase, and most measurable progress builds from 5mg onward, month by month.

Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.

06 · Using the pen

How do you use and store an injectable pen?

Mounjaro is injected under the skin once a week, on the same day each week, at any time of day, with or without food. Licensed sites are the stomach area, the front of the thigh, or the back of the upper arm if someone else gives the injection. Rotate the site with each dose.¹

Keep pens in a fridge at 2–8°C and never freeze them. Once in use, a pen can be kept out of the fridge at a temperature not above 30°C for up to 30 days after first use, and must then be thrown away. Do not use a pen that has been above 30°C or has been frozen.¹³ Needles, a sharps bin and injection guidance come with every order.

07 · NHS access

Can you get a GLP-1 injectable on the NHS?

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.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.