Mounjaro (Tirzepatide): Complete UK Guide
How it works, clinical results, costs, side effects, and where to buy from verified UK pharmacies.
22.5%
Average weight loss (15mg dose)¹
Weekly
Injection frequency
From £149
Per month (UK providers)
Dual GIP/GLP-1
Mechanism of action
What Is Mounjaro?
Mounjaro (tirzepatide) is a prescription weight loss injection manufactured by Eli Lilly. It was approved by the National Institute for Health and Care Excellence (NICE) in 2024 for weight management in adults with a BMI of 30 or above (or 27 with weight-related comorbidities).²
Unlike older weight loss medications, Mounjaro works on two hormone receptors simultaneously — GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide). This dual mechanism helps reduce appetite, slow gastric emptying, and improve blood sugar regulation.
In the landmark SURMOUNT-1 clinical trial published in the New England Journal of Medicine, participants taking the highest dose (15mg) lost an average of 22.5% of their body weight over 72 weeks — the largest weight reduction seen in any GLP-1 receptor agonist trial to date.¹
Dosing Schedule
Mounjaro is injected once weekly. The dose is gradually increased every 4 weeks to minimise side effects, as outlined in the Summary of Product Characteristics (EMC).³
Who Is Eligible?
Adults aged 18 or over
BMI of 30 or above (obese), or BMI of 27+ with at least one weight-related condition (e.g. type 2 diabetes, high blood pressure, sleep apnoea)
Must complete an online consultation with a prescriber
Not currently pregnant or breastfeeding
No personal or family history of medullary thyroid cancer or MEN2 syndrome
Based on NICE TA924 eligibility criteria.²
Side Effects
The most common side effects are gastrointestinal and usually improve as your body adjusts. Data is from the SURMOUNT-1 trial¹ and the EMC SmPC.³
MHRA Safety Alert: GLP-1 receptor agonists carry a small risk of acute pancreatitis. Seek immediate medical attention if you experience severe, persistent abdominal pain. Read the MHRA guidance →⁴
How Much Does Mounjaro Cost in the UK?
Mounjaro is currently available as a private prescription from online pharmacies. Costs vary by provider and dose, with starting prices typically ranging from £149 to £179 per month for the initial 2.5mg dose. Higher doses cost more as you progress through the titration schedule.
All prices include the cost of an online consultation with a prescriber. Some providers offer bundle discounts for multi-month supplies.
Explore Mounjaro in Detail
Dosage Guide
Full titration schedule from 2.5mg to 15mg, injection instructions, and storage.
Read more →Side Effects
Common and serious side effects with clinical trial data and management tips.
Read more →Cost & Pricing
Private prescription prices by dose, NHS availability, and money-saving tips.
Read more →Important Medical Information
This website provides general information about weight loss medications for educational purposes only. It is not intended as medical advice, diagnosis, or treatment. Always consult your GP or qualified healthcare professional before starting any weight loss medication. Individual results may vary.
WhichWeightMeds.org is an independent comparison platform and is not affiliated with any pharmacy, manufacturer, or healthcare provider. We do not prescribe, sell, or dispense medications.
Sources & References
- 1Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1) — New England Journal of Medicine, 2022 (Accessed February 2026)View source
- 2Tirzepatide for Weight Management — NICE Technology Appraisal TA924 — National Institute for Health and Care Excellence (Accessed February 2026)View source
- 3Mounjaro (tirzepatide) Summary of Product Characteristics — Electronic Medicines Compendium (EMC) (Accessed February 2026)View source
- 4GLP-1 receptor agonists — safety review — Medicines and Healthcare products Regulatory Agency (MHRA) (Accessed February 2026)View source