Weight Loss Medication UK: Mounjaro, Saxenda & Prescription Options
Prescription weight loss medication is designed to work alongside — not instead of — lifestyle changes. For eligible adults, it can produce weight loss significantly beyond what diet and exercise alone achieves.
20.9%
Average body weight loss with Mounjaro 15mg (SURMOUNT-1 trial, 72 weeks)
8–9%
Average body weight loss with Saxenda alongside diet and exercise (SCALE trial, 56 weeks)
3–5%
Additional weight loss with orlistat compared to lifestyle changes alone
Prescription weight loss medications are MHRA-approved treatments indicated for adults with obesity or excess weight and at least one related health condition. They are designed as adjuncts to a reduced-calorie diet and increased physical activity — not as standalone solutions.
This guide covers all currently available MHRA-approved prescription weight loss options in the UK, how they work, what the clinical evidence shows, and how to access treatment through a GPhC-registered pharmacy.
Who Might Benefit from Prescription Weight Loss Treatment?
Prescription weight loss medication is appropriate for adults for whom lifestyle modifications alone have not produced clinically meaningful weight loss, and who meet NICE eligibility criteria (see below). Weight management is complex, and for many people biological factors — including hormonal regulation of appetite, genetics, and metabolic adaptation — make sustained weight loss extremely difficult without additional support.
Groups who may benefit include:
- Adults with a BMI of 30 or above (obesity)
- Adults with a BMI of 27–29.9 (overweight) alongside a weight-related health condition such as type 2 diabetes, hypertension, or dyslipidaemia
- People who have made consistent, genuine lifestyle changes without achieving sufficient weight loss
- Those whose excess weight poses significant risk to metabolic, cardiovascular, or musculoskeletal health
Weight gain associated with reduced activity — including periods of reduced mobility or lifestyle disruption — can be difficult to reverse through diet and exercise alone. Read more about the causes of weight gain and health risks in our full guide →
1. Mounjaro (Tirzepatide) — Dual GIP & GLP-1 Receptor Agonist
New — most effective injectable currently available in the UK. Mounjaro (tirzepatide) was approved by the MHRA in November 2023 for chronic weight management and represents a step change in treatment efficacy.
How it works
Mounjaro is a dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist. By activating both incretin receptors simultaneously, it suppresses appetite, slows gastric emptying, and improves insulin sensitivity more effectively than GLP-1 agonists alone.
Clinical evidence
The SURMOUNT-1 phase III trial (published in the New England Journal of Medicine, 2022) demonstrated that tirzepatide 15mg achieved an average body weight reduction of 20.9% over 72 weeks in adults with obesity without diabetes. Key outcomes:
- 91% of participants lost at least 5% of body weight
- 57% of participants lost 20% or more of body weight
- Weight loss approximately double that seen with GLP-1 agonists alone
NICE approved tirzepatide for weight management in England in January 2024 (TA1026).
Administration
Mounjaro is administered as a once-weekly subcutaneous injection using a pre-filled autoinjector pen. Dosing begins at 2.5mg and is escalated gradually over approximately 20 weeks to the 15mg maintenance dose, allowing tolerability to build.
Prescription and access
Mounjaro is a prescription-only medicine (POM). It is available online via GPhC-registered pharmacies following a medical consultation. Read the full Mounjaro guide →
2. Saxenda (Liraglutide) — GLP-1 Receptor Agonist
Saxenda (liraglutide 3mg) is a once-daily injectable GLP-1 receptor agonist that has been available in the UK since 2016. It is MHRA-approved, FDA-approved, and recommended by NICE under TA664.
Clinical evidence
The SCALE Obesity and Prediabetes trial (New England Journal of Medicine, 2015) showed that liraglutide 3mg, alongside a reduced-calorie diet and increased physical activity, achieved an average weight loss of approximately 8–9% over 56 weeks. Around 60% of participants lost at least 5% of body weight, and approximately 33% lost 10% or more.
Administration
Saxenda is administered as a once-daily subcutaneous injection. The dose is escalated over five weeks — starting at 0.6mg and increasing to the 3mg maintenance dose — to minimise gastrointestinal side effects. The injection is typically given in the abdomen, thigh, or upper arm.
Prescription and access
Saxenda is a prescription-only medicine. It requires a medical consultation before prescription. Read the full Saxenda guide →
3. Orlistat — Lipase Inhibitor
Orlistat is an oral weight loss medicine that works by blocking approximately one-third of dietary fat from being absorbed in the gut. Unlike the injectable GLP-1 and dual agonist options, it does not affect appetite or hormonal regulation directly.
Clinical evidence
Orlistat produces approximately 3–5% additional weight loss compared to lifestyle changes alone. It is less effective than the injectable options but remains a useful option for patients who cannot use or prefer not to use injections.
Forms and dosing
- Xenical 120mg — prescription-only; taken with each main fat-containing meal, up to 3 times daily
- Alli 60mg — available over the counter for adults with a BMI of 28 or above
Side effects
The most common side effects are gastrointestinal and include oily or fatty stools, oily spotting on underwear, and urgent bowel movements. These effects are significantly reduced by following a low-fat diet (less than 30% of calories from fat).
Side-by-Side Comparison
| Feature | Mounjaro | Saxenda | Orlistat |
|---|---|---|---|
| Mechanism | Dual GIP & GLP-1 receptor agonist | GLP-1 receptor agonist | Lipase inhibitor |
| Average weight loss | ~20.9% body weight | ~8–9% body weight | ~3–5% additional vs lifestyle |
| Administration | Weekly injection | Daily injection | Oral capsule with meals |
| Prescription required | Yes (POM) | Yes (POM) | 120mg: Yes / 60mg: OTC |
| Main side effects | Nausea, diarrhoea (usually early) | Nausea, diarrhoea (usually early) | Oily stools, urgent bowel movements |
| BMI eligibility | 30+ or 27+ with comorbidity | 30+ or 27+ with comorbidity | 28+ (OTC) or 30+ (prescription) |
Eligibility Criteria
NICE guidelines (CG189) set out eligibility criteria for prescription weight loss medication. Patients generally need to meet all of the following:
- BMI of 30 or above, or BMI of 27–29.9 with at least one weight-related comorbidity (such as type 2 diabetes, hypertension, or hyperlipidaemia)
- Have not achieved sufficient weight loss through lifestyle changes alone
- Committed to ongoing dietary modification and increased physical activity
- No contraindications to the specific medication being considered
- Full medical consultation completed before any prescription is issued
Mounjaro and Saxenda are not appropriate for everyone. Both are contraindicated in pregnancy, in people with a personal or family history of medullary thyroid carcinoma, and in those with certain other conditions. A full clinical assessment is required before prescribing.
How to Access Prescription Weight Loss Medication Online
Access Doctor is a GPhC-registered pharmacy (registration #9011198). Treatment can be accessed entirely online through the following steps:
1
Complete an online consultation
A short medical questionnaire covering your health history, current medications, weight, height, and treatment goals. Takes approximately 5 minutes.
2
Review by a GPhC-registered prescriber
Your consultation is assessed by a pharmacist independent prescriber registered with the GPhC. They review your answers against clinical eligibility criteria.
3
Prescription issued if eligible
If clinically appropriate, a prescription is issued electronically. If you are not suitable, you will be advised accordingly.
4
Medication dispatched
Medication is dispatched in discreet packaging, typically with next-day delivery within the UK.
Ready to explore your options?
Complete a free online consultation with a GPhC-registered prescriber (pharmacy #9011198). Treatment dispatched with discreet next-day delivery if eligible.
Explore Weight Loss TreatmentsFrequently Asked Questions
What weight loss medications are available in the UK?
The MHRA-approved prescription weight loss medications currently available in the UK are Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist approved in November 2023; Saxenda (liraglutide 3mg), a once-daily GLP-1 agonist; and orlistat, an oral lipase inhibitor available as prescription-strength Xenical (120mg) or over-the-counter Alli (60mg). Wegovy (semaglutide 2.4mg) is also MHRA-approved though availability varies. All injectable options require a prescription from a qualified prescriber.
Do I need a prescription for weight loss injections?
Yes. Mounjaro and Saxenda are both prescription-only medicines (POMs) in the UK. They cannot legally be dispensed without a valid prescription issued by a qualified prescriber following a medical assessment. Access Doctor’s GPhC-registered pharmacist independent prescribers can issue prescriptions online following a consultation.
What BMI qualifies for prescription weight loss medication?
NICE guidelines recommend considering prescription weight loss medication for adults with a BMI of 30 or above, or a BMI of 27–29.9 if at least one weight-related health condition is present (such as type 2 diabetes, hypertension, high cholesterol, or obstructive sleep apnoea). Full clinical eligibility must be confirmed through a medical consultation.
How effective is prescription weight loss medication?
Effectiveness varies by treatment. In the SURMOUNT-1 trial, Mounjaro 15mg produced an average body weight loss of 20.9% over 72 weeks. Saxenda produced an average of 8–9% weight loss over 56 weeks in the SCALE trial. Orlistat produces approximately 3–5% additional weight loss versus lifestyle changes alone. All treatments are most effective when combined with a reduced-calorie diet and increased physical activity.
Are there side effects from weight loss medication?
The most common side effects of Mounjaro and Saxenda are gastrointestinal — including nausea, vomiting, diarrhoea, and constipation — particularly during dose escalation. These typically improve as the body adjusts. Orlistat’s main side effects are oily or fatty stools and urgent bowel movements, which are significantly reduced by following a low-fat diet. All side effects should be discussed with a prescriber at the consultation stage.
Can I get prescription weight loss medication online?
Yes, through a GPhC-registered pharmacy with qualified prescribers. Access Doctor (GPhC #9011198) provides online consultations assessed by pharmacist independent prescribers. If clinically eligible, a prescription is issued and medication is dispatched with next-day delivery. It is not legal or safe to obtain prescription weight loss medications without a valid prescription from a qualified UK prescriber.
References
- NICE. Obesity: identification, assessment and management (CG189). National Institute for Health and Care Excellence, 2014 (updated 2023). nice.org.uk/guidance/cg189
- NICE. Tirzepatide for managing overweight and obesity (TA1026). National Institute for Health and Care Excellence, 2024. nice.org.uk/guidance/ta1026
- NICE. Liraglutide for managing overweight and obesity (TA664). National Institute for Health and Care Excellence, 2020. nice.org.uk/guidance/ta664
- Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity. N Engl J Med. 2022;387(3):205–216. doi:10.1056/NEJMoa2206038
- Pi-Sunyer X, et al. A randomized, controlled trial of 3.0mg of liraglutide in weight management. N Engl J Med. 2015;373(1):11–22. doi:10.1056/NEJMoa1411892
- NHS. Treatment: Obesity. NHS, 2023. nhs.uk/conditions/obesity/treatment
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Mounjaro and Saxenda are prescription-only medicines (POMs) and must only be used under medical supervision following a clinical assessment by a qualified prescriber. Do not start, stop, or change any medication without consulting a healthcare professional. Access Doctor is registered with the General Pharmaceutical Council (GPhC #9011198).