Reviewed by a GPhC-registered Pharmacist at Newdays Pharmacy
Quick Answer: Mounjaro (tirzepatide) is an MHRA approved injectable weight loss medicine available in the UK. It is a weekly self injection that targets two gut hormones (GLP-1 and GIP) to reduce appetite and food intake. It is available on prescription only and must be used as part of a supervised weight management programme.
What Is Mounjaro?
Mounjaro is the brand name for tirzepatide, a dual GLP-1 and GIP receptor agonist manufactured by Eli Lilly. It was originally developed for the treatment of type 2 diabetes (where it is also licensed under the same brand name in the UK) and was subsequently approved by the MHRA for chronic weight management in adults.
Tirzepatide works by mimicking two gut hormones simultaneously: GLP-1 (glucagon like peptide 1) and GIP (glucose dependent insulinotropic polypeptide). By activating both receptors, it reduces appetite, slows gastric emptying, and reduces overall calorie consumption more effectively than medicines acting on GLP-1 alone.
How Effective Is Mounjaro for Weight Loss?
In the SURMOUNT 1 phase 3 clinical trial, adults with obesity or overweight (without type 2 diabetes) who received tirzepatide 15 mg (the highest approved dose) achieved an average weight reduction of 22.5% over 72 weeks, compared to 2.8% in the placebo group. Lower doses (5 mg and 10 mg) also demonstrated clinically significant weight loss.
These are clinical trial results under controlled conditions. Real world outcomes vary. The best results are achieved when Mounjaro is combined with a reduced calorie diet and regular physical activity.
Who Can Take Mounjaro for Weight Loss?
Mounjaro for weight management is indicated for adults with:
- A BMI of 30 kg/m² or above (obesity), OR
- A BMI of 27 kg/m² or above (overweight) and at least one weight related comorbidity (for example type 2 diabetes, hypertension, dyslipidaemia, obstructive sleep apnoea, or cardiovascular disease)
It should be used alongside a reduced calorie diet and increased physical activity as part of a structured weight management programme.
Who Should Not Take Mounjaro?
Mounjaro is not suitable for everyone. It is contraindicated in individuals with:
- A personal or family history of medullary thyroid carcinoma (MTC)
- Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)
- Known hypersensitivity to tirzepatide
- Pregnancy or breastfeeding: it must not be used during pregnancy
It should be used with caution in people with a history of pancreatitis, diabetic retinopathy, or severe gastrointestinal disease. Always undergo a thorough clinical assessment before starting treatment.
How Is Mounjaro Taken?
Mounjaro is administered as a once weekly subcutaneous (under the skin) injection using a prefilled auto injector pen. Recommended injection sites are the stomach, thigh, or upper arm. The starting dose is 2.5 mg once weekly for four weeks, then increased by 2.5 mg every four weeks as tolerated, up to a maximum of 15 mg weekly.
This gradual dose escalation is important to minimise gastrointestinal side effects such as nausea and diarrhoea.
What Are the Side Effects of Mounjaro?
The most common side effects reported in clinical trials are gastrointestinal:
- Nausea (most common, particularly during dose escalation)
- Diarrhoea
- Constipation
- Vomiting
- Abdominal pain
- Decreased appetite
These effects are typically mild to moderate and tend to improve over time. Serious but uncommon risks include pancreatitis, gallbladder disease, heart rate increase, and injection site reactions. Full side effect information is provided in the patient information leaflet.
Can I Get Mounjaro at a Pharmacy in Windsor or Reading?
Mounjaro is a prescription only medicine (POM) and cannot be purchased over the counter. It must be prescribed by a suitably qualified prescriber following a clinical assessment of eligibility.
At Newdays Pharmacy, our weight management service includes a consultation with a GPhC registered pharmacist prescriber or a referral pathway to an appropriate prescriber, as part of our managed weight loss programme. We serve patients across Windsor, Eton, Reading, Twyford, and surrounding areas in Berkshire and Buckinghamshire.
Clinical Disclaimer: This article is intended for general information only and does not constitute medical advice. Always consult a qualified healthcare professional before starting any treatment or medication. Information is accurate as of the date of publication and reviewed by a GPhC-registered pharmacist.
Frequently Asked Questions
No. Mounjaro (tirzepatide) and Ozempic (semaglutide) are different medicines, although both are weekly injections used for weight management. Ozempic is licensed in the UK for type 2 diabetes; Wegovy (also semaglutide) is licensed for weight management. Mounjaro acts on two hormonal pathways (GLP-1 and GIP) whereas Ozempic and Wegovy act on GLP-1 alone.
Many people begin to notice reduced appetite within the first few weeks. Meaningful weight loss is typically apparent after eight to twelve weeks of treatment at therapeutic doses, with the greatest effects seen at six to twelve months.
Weight regain is common after stopping GLP-1/GIP receptor agonists. Long-term treatment is usually required to maintain weight loss. Stopping treatment should only be done in discussion with your prescriber.