Tirzepatide is one of the most talked-about medications in the UK right now — and for good reason. Clinical trials have shown it to be the most effective weight loss injection currently available, with results that were previously only achievable through bariatric surgery. But what exactly is Tirzepatide, how does it work, and how can you access it in the UK?

What is Tirzepatide?

Tirzepatide is the active ingredient in Mounjaro, a once-weekly weight loss injection developed by Eli Lilly. It is a novel dual-action medication that belongs to a new class of drugs called GIP/GLP-1 receptor agonists — making it distinct from older GLP-1 only treatments like Semaglutide (Ozempic/Wegovy).

Tirzepatide was MHRA-approved in the UK in November 2023 for chronic weight management in eligible adults, and has since become one of the most prescribed weight loss treatments in the country.

How Does Tirzepatide Work?

Tirzepatide works by mimicking two naturally occurring hormones involved in appetite regulation and metabolism:

GIP (Glucose-dependent Insulinotropic Polypeptide) — a hormone released after eating that signals satisfaction and plays a role in fat metabolism. By activating GIP receptors, Tirzepatide enhances feelings of fullness and may support the body’s ability to use stored fat for energy.

GLP-1 (Glucagon-like Peptide-1) — a hormone that slows stomach emptying, reduces appetite signals in the brain and stimulates insulin release. GLP-1 receptor activation is the mechanism shared with Semaglutide (Wegovy/Ozempic).

By targeting both receptors simultaneously, Tirzepatide produces a stronger and more comprehensive effect on appetite and metabolism than single-receptor treatments.

What Do the Clinical Trials Show?

The SURMOUNT clinical trial programme provided compelling evidence for Tirzepatide’s effectiveness:

At the 10mg dose, average weight loss was approximately 19.5% of body weight over 72 weeks
At the 15mg dose, average weight loss reached 20.9% of body weight — with some participants losing over 25%
Results were significantly superior to placebo and to Semaglutide (Wegovy) in comparative studies

To put this in context, a person starting at 100kg could expect to lose approximately 20kg on Tirzepatide at the highest dose over 18 months — results that historically required surgical intervention.

Who is Tirzepatide Suitable For?

Tirzepatide (Mounjaro) may be suitable for adults who:

Have a BMI of 30 or above, or
Have a BMI of 27 or above with at least one weight-related health condition (such as high blood pressure, type 2 diabetes or high cholesterol)
Are committed to making lifestyle changes alongside medication

It is not suitable for people with a personal or family history of medullary thyroid cancer, MEN2 syndrome, or those who are pregnant or breastfeeding.

How Do You Take Tirzepatide?

Tirzepatide is administered as a once-weekly subcutaneous injection using a pre-filled auto-injector pen. It is typically injected into the abdomen, upper thigh or upper arm.

Treatment begins at 2.5mg once weekly and increases gradually over several months to a maximum of 15mg, depending on response and tolerability.

How to Get Tirzepatide in the UK

Tirzepatide (Mounjaro) is available on private prescription in the UK through regulated online pharmacies including MedExpress. NHS access remains very limited at present.

At MedExpress, you can complete a free online consultation with our UK-based clinical team and, if eligible, receive your Tirzepatide prescription delivered discreetly to your door — with no GP appointment required. Prices start from £129 per month.

👉 Buy Tirzepatide (Mounjaro) UK — from £129

What is Tirzepatide UK? How It Works, Benefits & Where to Get It