This guide is the map. It sets out each licensed injection, Mounjaro, Wegovy and Saxenda, what it is, how it works, how often you take it, and how NHS access compares. It does not rank them, because the right option is a clinical decision. Everything here is drawn from the UK Summaries of Product Characteristics, NICE and the NHS.
What a weight loss injection actually is
All three licensed weight-loss injections belong to a family of medicines that act on gut hormone receptors. Saxenda and Wegovy are GLP-1 receptor agonists, and Mounjaro is a dual GIP and GLP-1 receptor agonist137. These hormones are released when you eat and act on the brain regions that control appetite, so the medicines reduce hunger and increase the feeling of fullness 13.
They are all given by subcutaneous injection, meaning under the skin of the abdomen, thigh or upper arm, and all are prescription-only medicines48. None of them is a standalone fix. Both the SmPCs and NICE describe them as an adjunct to a reduced-calorie diet and increased physical activity, not a replacement for those things 49.
They also share a broad safety profile. The SmPCs for all three carry the same headline cautions: acute pancreatitis, gallbladder problems, dehydration from gut side effects, and an increased risk of low blood sugar if combined with a sulphonylurea or insulin in people with type 2 diabetes 1116. None is used in pregnancy 43. The differences between them are real but sit on top of this common foundation, which is why a prescriber weighs them up case by case rather than declaring one the winner.
If you want the underlying biology, our guide on how GLP-1 and GIP medications actually work explains the incretin system. The sections below take each licensed injection in turn.
Mounjaro (tirzepatide)
Mounjaro is the brand name for tirzepatide, the only dual GIP and GLP-1 receptor agonist of the three 7. It is a once-weekly injection, licensed for weight management in adults with a BMI of 30 kg/m2 or above, or 27 to under 30 with a weight-related condition, and separately for type 2 diabetes 4.
It is started at 2.5 mg once weekly and increased in stages to a maintenance dose of 5, 10 or 15 mg 10. The most common side effects are gastrointestinal, mainly nausea, which is usually mild to moderate and eases over time 11. Our complete Mounjaro guide covers it in full, and Mounjaro versus Wegovy compares the two weekly injections directly.
On the NHS in England, NICE recommends tirzepatide for adults with a BMI of at least 35 and a weight-related condition, and it can be used in primary care or specialist services, rolled out in phases 5. NICE judged that, alongside diet and exercise support, tirzepatide is more effective than that support alone 5. It is the newest of the three injections and the only dual agonist, which is the main reason it draws so much attention.
Wegovy (semaglutide)
Wegovy is a brand of semaglutide, a GLP-1 receptor agonist 12. The NHS lists semaglutide under the brands Wegovy for obesity and Ozempic and Rybelsus for type 2 diabetes, so Wegovy is the semaglutide product for weight management 12. It is a once-weekly injection 12.
On the NHS, NICE recommends semaglutide for weight management only within a specialist weight management service and for a maximum of two years, for adults with a BMI of at least 35, or 30 to 34.9 who meet the criteria for referral to such a service, plus a weight-related condition 14. Our guide on how Wegovy works covers semaglutide on its own.
NICE's review found that people lose more weight with semaglutide plus supervised support than with the support alone, that more weight is lost with semaglutide than with liraglutide, and that semaglutide may reduce the risk of cardiovascular disease 14. The NHS also notes semaglutide may be offered to people with obesity who have had a heart attack or stroke, or who have peripheral arterial disease 12. As with all of these medicines, it is used alongside diet and activity, not instead of them 9.
Saxenda (liraglutide)
Saxenda is the brand name for liraglutide, a GLP-1 receptor agonist 3. The clearest practical difference from the other two is the schedule: Saxenda is a daily injection, not weekly 15. It is started at 0.6 mg once daily and increased weekly in 0.6 mg steps to a maintenance dose of 3.0 mg daily 15.
It is licensed for adults with a BMI of 30 or above, or 27 to under 30 with a weight-related condition, and for adolescents from age 12 in defined circumstances 3. As with the others, the SmPC advises stopping if at least 5 percent of body weight has not been lost after 12 weeks on the 3.0 mg dose 3. The common side effects are again mainly gastrointestinal, reported in about 68 percent of people in the trials, usually mild to moderate and easing over the first weeks 16. Our guide on the Saxenda weight loss injection covers it in more detail.
In the SCALE trial programme, people on liraglutide lost on average 8.0 percent of their body weight at 56 weeks, compared with 2.6 percent on placebo, a difference of about 5.4 percent, alongside diet and activity 19. As noted above, NICE's later comparison found more weight is lost with semaglutide than with liraglutide 14, which is part of why liraglutide is now used less often than the newer options. It remains a licensed and evidence-based choice, and the daily schedule suits some people.
How the three injections compare
The table below sets out the headline differences. It is a starting point for a conversation with a prescriber, not a ranking. Each medicine has its own full SmPC, its own contraindications and its own side-effect profile, and the right choice depends on your medical history and how you tolerate treatment.
Note that all three share the same broad safety themes. The SmPCs for all of them carry cautions about acute pancreatitis, gallbladder problems, dehydration from gut side effects, and an increased risk of low blood sugar if combined with a sulphonylurea or insulin in people with type 2 diabetes 51116. None should be used in pregnancy 43.
| Mounjaro | Wegovy | Saxenda | |
|---|---|---|---|
| Active ingredient | Tirzepatide 7 | Semaglutide 12 | Liraglutide 3 |
| Receptors | GIP and GLP-1 7 | GLP-1 12 | GLP-1 3 |
| Schedule | Weekly injection 10 | Weekly injection 12 | Daily injection 15 |
| Maintenance dose | 5, 10 or 15 mg 10 | Set by SmPC | 3.0 mg daily 15 |
| NHS weight route | Primary care or specialist 5 | Specialist, up to 2 years 14 | Specialist tier 3, narrow criteria 17 |
NHS access and who can get them
NHS access is the area where the three diverge most, and it is much narrower than the licence in every case. In England, NICE recommends tirzepatide for adults with a BMI of at least 35 and a weight-related condition, rolled out in phases 5. Semaglutide is recommended only within a specialist service and for up to two years 14. Liraglutide is recommended only for a narrow group: a BMI of at least 35, non-diabetic hyperglycaemia and a high risk of cardiovascular disease, in a specialist tier 3 service 17.
Access also differs by nation. In Scotland, the SMC accepts tirzepatide for restricted use under a patient access scheme 6. In Wales, tirzepatide for weight loss is currently started only through NHS specialist weight management services 18. The practical result is that many people who are eligible by licence are not yet eligible on the NHS, which is why the private route exists, and why checking your nation's criteria matters before assuming how you will access treatment.
Because NHS eligibility is narrow, many people who want treatment look at the private route, which is self-funded. If you go that way, the same safeguards apply: a proper clinical assessment of whether the medicine suits you, supply from a registered pharmacy, and honest disclosure of your medical history 8. All three medicines share a 5 percent weight-loss review point, at six months for the injections that NICE recommends in this way, so the first months are also the period that decides whether ongoing treatment is justified 5.
Whichever medicine and route, the NHS advises buying only from a registered pharmacy, because some websites sell fake weight-loss medicines 8. If you are weighing up whether an injection is right for you at all, our guide on recognising when GLP-1 treatment is not right for you is a useful counterweight to the hype.
Frequently asked questions
Which weight loss injection is best?
There is no single best injection; it depends on your medical history, how you tolerate treatment, and what you can access. Mounjaro acts on two receptors and Wegovy and Saxenda on one, and Saxenda is daily while the others are weekly 7315. Each has its own SmPC and side-effect profile. The choice is a clinical decision made with a prescriber, not a ranking 4.Are weight loss injections available on the NHS?
Yes, but access is limited and criteria-based, and it differs by medicine and nation. In England, NICE recommends tirzepatide for a BMI of at least 35 with a weight-related condition (phased), semaglutide only in a specialist service for up to two years, and liraglutide only for a narrow high-risk group 51417. Many people who qualify by licence do not yet qualify on the NHS.What is the difference between weekly and daily injections?
Mounjaro and Wegovy are injected once a week, while Saxenda is injected once a day 101215. A weekly injection means fewer injections to remember; a daily one is more frequent. Neither is automatically better. The schedule is one of several factors, alongside how the medicine works and how you tolerate it, that a prescriber weighs up with you.Do all weight loss injections have the same side effects?
They share the same broad pattern. The most common effects for all three are gastrointestinal, mainly nausea, usually mild to moderate and easing over the first weeks 1116. All carry SmPC cautions about pancreatitis, gallbladder problems and dehydration 53. The exact frequencies differ between medicines, which is one reason the choice is individual.Do I have to stay on a weight loss injection forever?
These medicines work while you take them, and appetite tends to return when they stop, so weight regain is common. NICE builds in review points, such as checking for at least 5 percent weight loss before continuing, and for semaglutide on the NHS treatment is limited to a maximum of two years 14. The NHS advises not stopping suddenly and discussing it with your doctor first 2. How long you stay on treatment is a clinical decision, not a life sentence.Your next step
The UK has three licensed weight-loss injections: Mounjaro and Wegovy weekly, Saxenda daily. They are related medicines with shared safety themes and different details, and the right one, if any, depends on your health and what you can access. NHS eligibility is narrower than the licence and varies by nation and medicine.
If you are considering a weight-loss injection, speak to your GP or pharmacist about NHS eligibility, or start a consultation with a clinician who can review your medical history and explain which options are appropriate for you. Bring an honest picture of your health and any other medicines you take, because that is what lets a prescriber match you to the right option safely. And whatever you decide, always use a registered pharmacy.
Disclaimer
This guide is for general information only and does not constitute medical advice, diagnosis or treatment. The information here describes general clinical context based on UK regulatory sources cited above; it is not a recommendation for any specific medicine or treatment, which can only be made by a prescriber following individual assessment.
If you are considering treatment, speak to your GP or pharmacist, or arrange a consultation with a Cloud Pharmacy clinician. Prescription-only medicines are issued only after clinical assessment and where appropriate.
If you experience side effects from any medicine, you can report them through the Yellow Card scheme at yellowcard.mhra.gov.uk.
References
- Mounjaro SmPC 5.1
- Semaglutide (Wegovy)
- Saxenda SmPC 4.1, 5.1
- Mounjaro SmPC 4.1
- TA1026 1 Recommendations
- SMC2653
- Mounjaro SmPC 5.1 mechanism
- Tirzepatide, registered pharmacy
- Medicines and surgery
- Mounjaro SmPC 4.2
- Mounjaro SmPC 4.8
- Semaglutide brands/use
- TA875 1 Recommendations
- Saxenda SmPC 4.2
- Saxenda SmPC 4.8
- TA664 1 Recommendations
- WHC/2025/018
- Saxenda SmPC 5.1 (SCALE trial 1, week 56)
