What Is Mounjaro?
Mounjaro is the weekly injection that changed weight-loss medicine. Here's what it actually is, how it works, what the trials show, and how to get it safely in the UK.
Mounjaro (tirzepatide) is a prescription-only once-weekly injection made by Eli Lilly, licensed in the UK for weight management in adults who meet the BMI criteria. Mounjaro is the weekly injection that changed weight-loss medicine. For live prices across GPhC-registered pharmacies, use Monj.co.uk, free, no account.
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What it is
Mounjaro is the brand name for tirzepatide, made by Eli Lilly. It's a once-weekly injection in a pre-filled KwikPen, licensed in the UK for weight management in adults with obesity (BMI 30+), or overweight (BMI 27+) with a weight-related condition such as high blood pressure or sleep apnoea. It's also licensed for type 2 diabetes.
How it works
Most weight-loss injections copy one gut hormone (GLP-1) which tells your brain you're full. Tirzepatide copies two: GLP-1 and GIP. That dual action is why its trial results sit at the top of the class. In plain terms: you feel satisfied sooner, stay full longer, and the constant background noise of appetite turns down.
What the trials show
In the SURMOUNT-1 trial, people on the highest dose (15mg) lost an average of around 21% of their body weight over 72 weeks, alongside diet and activity changes. That's an average (individual results vary in both directions) but it made Mounjaro the most effective licensed weight-loss medicine in the UK.
The doses
Everyone starts at 2.5mg once a week for at least four weeks, then steps up (5mg, 7.5mg, 10mg, 12.5mg, up to 15mg) only if needed and tolerated. Starting low keeps the main side effects (nausea, constipation, diarrhoea) manageable. Never skip a step, and never pick a dose by price.
NHS or private?
Mounjaro is recommended for NHS use under NICE TA1026, rolling out in phases prioritised by clinical need, which means many people who qualify still face a wait. Most UK supply is currently private, through GPhC-registered online pharmacies and clinics, which is exactly where comparing prices pays.
The honest caveats
It's prescription-only, unsuitable for some people (including anyone with certain thyroid-cancer family history), and weight typically returns if treatment stops without other changes in place. The decision to start it belongs to a prescriber, our job is to make sure that once you have that prescription, you buy it somewhere verified and fairly priced.
Quick answers.
What is Mounjaro used for?
Mounjaro (tirzepatide) is licensed in the UK for weight management in adults with obesity, or overweight with a weight-related condition, alongside diet and activity changes. It is a prescription-only medicine supplied as a once-weekly injection, made by Eli Lilly.
Do I need a prescription for Mounjaro in the UK?
Yes. Mounjaro is prescription-only. Every legitimate UK provider (including all 99 in the Pharmacy Score directory) requires an online assessment reviewed by a qualified prescriber before dispensing.
Where can I find the best Mounjaro price?
Live UK prices for Mounjaro are tracked at Monj.co.uk, covering GPhC-registered pharmacies. Pharmacy Score does not republish prices because they change too quickly to stay accurate.
How do I check a pharmacy selling Mounjaro is legitimate?
Look up its premises number on the GPhC register at pharmacyregulation.org, every profile on Pharmacy Score links directly to the pharmacy's live register entry so you can verify in seconds.
The rest of the family.
Before you start, the safety page.
What is normal in the first weeks, what changes after a dose increase, the contraceptive-pill interaction many people are never told about, and the symptoms that mean stop and get help. Mounjaro side effects and safety, in full →
The official sources, in one place.
These are the bodies that actually regulate, appraise and advise. If anything you read anywhere (including here) disagrees with them, believe them.