The best weight-loss injections in 2026

Jump to: Comparison at a glance | Tirzepatide (Mounjaro) | Semaglutide (Wegovy) | Liraglutide (Saxenda) | NHS vs private access | Side effects comparison | Cost analysis | How to choose | Medications in development | Frequently asked questions | Take home message

Based on clinical trial data, the most effective weight-loss injection available in the UK in 2026 is tirzepatide (Mounjaro), which supports an average weight loss of 22.5% of starting body weight after 72 weeks at the maximum 15 mg dose.¹

However, the gap between Mounjaro and Wegovy has narrowed. The MHRA approved a higher dose of 7.2 mg of Wegovy in January 2026, which achieved an average weight loss of 20.7%. That is less than two percentage points behind Mounjaro.²

The three main weight-loss injections currently available in the UK are tirzepatide (Mounjaro), semaglutide (Wegovy), and liraglutide (Saxenda).

Cost is now a bigger factor than it was a year ago, after Eli Lilly raised Mounjaro’s UK list price by up to 170% in September 2025, making Wegovy the more affordable option for many people with comparable weight-loss results.

Weight-loss injections: comparison at a glance

1. Tirzepatide (Mounjaro)

Tirzepatide, marketed as Mounjaro in the UK, remains the most effective weight-loss injection based on clinical trial data. It also became available on the NHS for weight management in June 2025, though access remains highly restricted and is reserved for individuals with the greatest clinical need.

How Mounjaro works

Mounjaro mimics two hormones: GLP-1 and GIP. This dual action reduces appetite and slows gastric emptying (the rate at which food leaves your stomach) more effectively than medications targeting GLP-1 alone.¹

The medication starts at 2.5 mg per week, increasing gradually to maintenance doses of 5 mg, 10 mg, or 15 mg based on individual response and tolerability.

Clinical evidence

The SURMOUNT-1 trial found that participants without diabetes lost an average of 22.5% of body weight at the 15 mg dose after 72 weeks.

91% achieved at least 5% weight loss, and 57% achieved 20% or more.¹ A direct comparison trial published in the New England Journal of Medicine in 2025 confirmed that tirzepatide produces greater weight loss than semaglutide 2.4 mg when compared head-to-head.³

Follow-up data from the SURMOUNT-4 trial shows weight loss is maintained at 88 weeks with continued use.⁴

Who can take Mounjaro?

NICE approved Mounjaro for weight management (TA1026) in adults with a BMI of 35 or above with weight-related health conditions, or a BMI of 30 or above with specific comorbidities.⁵

You can’t take Mounjaro if you have a personal or family history of medullary thyroid cancer or Multiple Endocrine Neoplasia syndrome type 2.

People with a history of pancreatitis or severe gastrointestinal disease need careful assessment before starting. The MHRA issued a Drug Safety Update in January 2025 specifically about monitoring and managing gastrointestinal side effects with tirzepatide.⁶

Important note on contraception: The MHRA has warned that Mounjaro may reduce the effectiveness of the combined oral contraceptive pill.

If you take the pill, use an additional barrier method (such as condoms) while on Mounjaro, or consider switching to a non-oral contraceptive like patches or an IUD.

The September 2025 price increase

Eli Lilly raised Mounjaro’s UK list price from September 2025 to bring it closer to global pricing levels. The highest dose (15 mg) saw the steepest increase, with list prices rising from £122 to £330 per four-week pen.

In practice, private prescription costs typically range from £149 for the initial 2.5 mg dose to £300–375 for the 15 mg maintenance dose, depending on the provider. This is a large increase from the pre-September prices of £92–122.

This price change has led many people to reconsider Wegovy as an alternative, particularly now that the higher 7.2 mg dose is available, with comparable weight-loss results.

2. Semaglutide (Wegovy)

Wegovy has been one of the most widely prescribed weight-loss injections worldwide since its UK launch. In January 2026, the MHRA approved a higher dose of 7.2 mg, which supports similar weight loss as Mounjaro.

Wegovy 7.2 mg

The STEP UP trial found that patients on Wegovy 7.2 mg lost an average of 20.7% of their body weight after 72 weeks, compared to 17.5% with the standard 2.4 mg dose.

A third of participants lost 25% or more of their body weight.² This higher dose is not a starting dose. It’s intended for people who have already reached and tolerated the 2.4 mg dose but need additional support to continue losing weight or have reached a plateau.

Currently, Wegovy 7.2 mg is administered as three consecutive 2.4 mg injections on the same day, using the existing 2.4 mg pen. A dedicated single-injection 7.2 mg pen is expected later in 2026.

How Wegovy differs from Ozempic

Both contain the drug semaglutide, but Wegovy uses higher doses specifically approved for weight loss. Ozempic’s maximum dose is 2 mg for type 2 diabetes.

Ozempic isn’t licensed for weight loss in the UK and should not be used off-label for this purpose. Wegovy follows a 16-week dose escalation schedule, starting at 0.25 mg and increasing gradually to the maintenance dose.

Clinical evidence

The STEP 1 trial showed participants achieved an average 14.9% weight loss over 68 weeks with semaglutide 2.4 mg.⁷

In a real-world UK setting, Second Nature’s published research in JMIR Formative Research found participants achieved 19.1% average weight loss at 12 months on a semaglutide-supported programme, with 77.7% achieving at least 10% weight loss.⁸

The SELECT trial demonstrated that semaglutide reduces major adverse cardiovascular events by 20% in people with existing heart disease and obesity.⁹

Advantages of Wegovy in 2026

Wegovy has three practical advantages over Mounjaro in the current market:

1 – Cost. Following Mounjaro’s price increase, Wegovy 2.4 mg is typically £150–250 per month, making it meaningfully cheaper than Mounjaro at maintenance doses. Wegovy 7.2 mg pricing is expected to be ~£250–300 per month.

2 – Cardiovascular evidence. Wegovy is currently the only weight-loss injection with cardiovascular benefits recognised on its label, based on the SELECT trial. Mounjaro has published trials showing cardiovascular benefits, but these haven’t been added to its licence.

3 – Safety track record. Wegovy has the longest real-world safety data of the newer weekly injections, with millions of doses administered globally since 2021.

3. Liraglutide (Saxenda)

Saxenda, containing liraglutide 3.0 mg, is a daily injection that remains available but has become less commonly prescribed as weekly alternatives have improved.

Clinical effectiveness

The SCALE trials demonstrated average weight loss of 5–7% over 56 weeks, which is modest compared to Mounjaro and Wegovy.¹⁰ 63% of participants achieved at least 5% weight loss, meeting the threshold for clinically meaningful health improvements.

When Saxenda might still be appropriate

Saxenda may be considered if you have not previously tolerated weekly GLP-1 medications, prefer daily dosing control (the ability to stop quickly if side effects occur), or if cost is a primary concern and Wegovy or Mounjaro are not affordable.

Some NHS Tier 3 services still primarily offer Saxenda due to established procurement pathways.¹¹ The daily injection schedule is harder to maintain long-term, with higher discontinuation rates than weekly alternatives.

NHS vs private access

NHS access in 2026

NHS access to weight-loss injections has expanded since 2025, but remains limited for most people.

Mounjaro (tirzepatide): NICE approved tirzepatide for weight management in early 2025 (TA1026), and NHS prescribing through primary care began in June 2025 under a phased 12-year rollout.⁵

Initial eligibility is restricted to people with a BMI of 40 or above (adjusted for ethnicity) and at least four weight-related health conditions.

These include type 2 diabetes, high blood pressure, cardiovascular disease, and obstructive sleep apnoea. This threshold will gradually expand to include more people over the coming years. In practice, availability varies by region and GP surgery.

Wegovy (semaglutide 2.4 mg): Available through NHS specialist Tier 3 weight management services, with eligibility typically requiring a BMI of 35 or above with health conditions. Waiting times for Tier 3 services range from 6–24 months depending on location.

Wegovy 7.2 mg: Not yet available on the NHS. NICE will need to complete a cost-effectiveness review before NHS coverage is confirmed, likely towards late 2026.

Saxenda: Available through some Tier 3 services under existing NICE guidance (TA664).¹¹

Private prescriptions

Private prescriptions remain the primary route for most people. Eligibility thresholds are lower than NHS criteria, typically requiring a BMI of 30 or above, or 27 with weight-related health conditions.

In January 2026, the General Pharmaceutical Council published updated inspection guidance specifically covering weight-loss medications, online pharmacies, and prescribing standards. This means reputable providers must now conduct more thorough assessments than a simple online questionnaire.

When choosing a private provider, check for CQC registration, qualified prescribers who conduct proper medical assessments, and ongoing monitoring throughout treatment.

Insurance

Most UK private health insurance excludes weight-loss medications.

Side effects comparison

Common side effects across all GLP-1 medications

Gastrointestinal side effects are the most common, particularly in the first few weeks and during dose increases. For most people, these improve as the body adjusts.

Nausea affects 30–44% of users initially. Constipation or diarrhoea may alternate. Fatigue and headaches occur in 10–15% of users, often related to reduced calorie intake rather than the medication itself.

Medication-specific patterns

A note on dysaesthesia: The STEP UP trial reported that 22.9% of people on Wegovy 7.2 mg experienced dysaesthesia, which includes tingling, numbness, or abnormal skin sensations. This is notably higher than the 6% seen with the 2.4 mg dose. However, 85.7% of these cases resolved while continuing treatment, and most were mild to moderate.²

Serious but rare side effects

Pancreatitis occurs in fewer than 0.2% of users but requires immediate medical attention if you experience severe abdominal pain.

Gallbladder problems, including gallstones, affect 1–2% of users, particularly with rapid weight loss. Changes in diabetic retinopathy may occur in people with existing diabetes and require monitoring.

Cost analysis

Updated private prescription costs (2026)

Prices vary by provider. Additional costs may include consultations (£50–150), blood tests (£50–100), and delivery charges.

Before September 2025, Mounjaro and Wegovy were priced similarly, making Mounjaro the more obvious choice given its superior weight-loss efficacy.

However, with Mounjaro’s price increasing and Wegovy 7.2 mg now available, Wegovy is likely to become more attractive for many patients.

Wegovy 7.2 mg achieves 20.7% weight loss at an estimated £250–300 per month, while Mounjaro’s highest dose achieves 22.5% at £300–375 per month.

For many people, the small additional weight loss with Mounjaro may not justify the higher cost, particularly over a 12–24 month treatment period where the total difference could amount to £600–1,800. This is a decision to make with your prescriber based on your individual circumstances, budget, and how your body responds to each medication.

How to choose the right weight-loss injection

Practical decision factors

If you need maximum weight loss and budget is not a constraint: Mounjaro at the 15 mg dose has the highest average efficacy in clinical trials.

If cost matters and you want comparable results: Wegovy 7.2 mg achieves close to Mounjaro’s efficacy at a lower price point. If you’re already on Wegovy 2.4 mg and have plateaued, stepping up to 7.2 mg may be worth discussing with your prescriber.

If you prefer daily dosing or need the lowest cost: Saxenda remains an option, though its efficacy is substantially lower than the other two.

Medical considerations

Your prescriber will assess contraindications, including thyroid cancer risk, pancreatitis history, and kidney function. Current medications need review.

If you take the oral contraceptive pill, be aware of the MHRA’s warning about Mounjaro potentially reducing its effectiveness. If you are planning a pregnancy, all GLP-1 medications must be stopped 2–3 months before conception.

Weight-loss medications in development

Several medications in late-stage trials may reach the UK within the next few years.

Retatrutide: the triple agonist

Eli Lilly’s retatrutide activates three hormone receptors: GLP-1, GIP, and glucagon. This is one more than Mounjaro’s dual action.

The first Phase 3 results (TRIUMPH-4, published in December 2025) showed an average weight loss of 28.7% at the 12 mg dose after 68 weeks. This is the highest figure recorded in any obesity treatment trial to date.¹⁴

Seven additional Phase 3 trials are expected to report results throughout 2026. If successful, regulatory submission could follow in late 2026 or early 2027, with UK availability potentially in 2027–2028.

A notable safety signal is dysaesthesia, reported in 20.9% of participants at the 12 mg dose. Discontinuation rates were also higher than for existing medications (18.2% at 12 mg vs ~7% for Mounjaro and Wegovy), partly driven by what Lilly described as ‘perceived excessive weight loss’.

Oral semaglutide (Wegovy pill)

Novo Nordisk launched an oral form of semaglutide for weight loss in the US in January 2026. The OASIS-4 trial found that the once-daily 25 mg tablet achieved approximately 16.6% weight loss over 64 weeks, approaching the weight loss achieved with the 2.4 mg Wegovy dose.

The MHRA is currently reviewing the oral formulation, with a decision expected towards late 2026. If approved, it would offer an alternative for people who prefer pills to injections.

CagriSema

Novo Nordisk’s combination of semaglutide with cagrilintide (an amylin analogue) targets two different pathways. Early results suggest 15–20% weight loss. UK availability is likely 2027–2029.

Orforglipron: daily pill from Eli Lilly

Eli Lilly’s oral GLP-1 medication has already been submitted to the FDA. Early data suggest 10–15% weight loss. If approved in the US, the UK submission would likely follow, with potential availability in 2027–2028.

Frequently asked questions

Which weight-loss injection is most effective in the UK?

Mounjaro (tirzepatide) at the 15 mg dose has the highest average efficacy in clinical trials, with 22.5% weight loss after 72 weeks.

However, the newer Wegovy 7.2 mg dose achieves 20.7%, a difference of less than two percentage points. The best choice for you depends on how your body responds, your budget, and your overall health profile.

Has Wegovy 7.2 mg closed the gap with Mounjaro?

Largely, yes. Before the 7.2 mg dose was approved, the gap between Wegovy (2.4 mg) and Mounjaro (15 mg) was roughly 5 percentage points. The higher Wegovy dose has narrowed this to less than two percentage points.

One in three people on Wegovy 7.2 mg lost 25% or more of their body weight, which is comparable to results previously seen only with Mounjaro and bariatric surgery.²

Why has Mounjaro’s price increased?

Eli Lilly raised Mounjaro’s UK list price from September 2025 to bring it closer to pricing in other countries.

When Mounjaro launched in the UK in 2024, it was priced lower than in other European markets to support faster access. The highest dose (15 mg) saw the largest increase, from £122 to £330 per four-week pen.

Can I switch from Mounjaro to Wegovy to save money?

Yes, switching is possible with your prescriber’s guidance. A 7-day washout period is usually recommended, and you would typically start at the relevant Wegovy dose based on your current Mounjaro dose. Your prescriber can advise on the safest way to transition.

Can I get weight-loss injections on the NHS?

NHS access has expanded but remains limited. Mounjaro became available through primary care from June 2025 under a phased rollout, initially for people with a BMI of 40+ and at least four weight-related health conditions.

Wegovy 2.4 mg is available through specialist Tier 3 services with 6–24 month waiting times. Most people currently access these medications privately.

What happens when I stop taking weight-loss injections?

A 2026 meta-analysis in the BMJ found that people regain a significant proportion of their lost weight within a year of stopping medication.¹²

Earlier data from the STEP-1 trial extension showed participants regained roughly two-thirds of lost weight within 12 months.¹³

Developing sustainable habits during treatment, such as better eating patterns, regular exercise, and consistent sleep, is important for maintaining results.

What’s the difference between Ozempic and Wegovy?

Both contain the drug semaglutide, but at different doses and for different purposes. Wegovy is approved for weight loss at doses up to 7.2 mg. Ozempic is approved for type 2 diabetes at a maximum of 2 mg. Ozempic is not licensed for weight loss in the UK.

How quickly will I see results?

Most people notice reduced appetite within the first week or two. Visible weight loss typically begins around weeks 4–8. Mounjaro and Wegovy users often see 5% weight loss by week 12. Maximum results occur at 12–18 months.

Does Mounjaro affect the contraceptive pill?

The MHRA has warned that Mounjaro may reduce the effectiveness of oral contraceptives. If you take the combined pill, use an additional method such as condoms, or discuss switching to a non-oral contraceptive (patches, IUD, or injection) with your GP.

When will the Wegovy pill be available in the UK?

The oral form of semaglutide (25 mg tablet) launched in the US in January 2026. The MHRA is reviewing it, with a decision expected towards the end of 2026. NHS availability would require a further NICE review.

When will retatrutide be available in the UK?

Retatrutide is still in Phase 3 trials. Seven trials are expected to report results throughout 2026. If all goes well, the regulatory submission could happen in late 2026 or early 2027, with UK approval and availability most likely in 2027–2028.

Are weight-loss injections safe for long-term use?

Current safety data support long-term use with appropriate monitoring. The longest studies span 2–4 years with reassuring safety profiles.

Regular monitoring should include kidney function, gallbladder health, and thyroid checks. For many people, the long-term cardiovascular and metabolic benefits of maintaining a healthy weight outweigh the risks of continued medication.

Take home message

Mounjaro remains the most effective weight-loss injection in the UK in 2026, with 22.5% average weight loss at the maximum dose. But the options available have changed considerably since 2025.

The MHRA approved Wegovy 7.2 mg in January 2026, which achieves 20.7% weight loss and has largely closed the gap with Mounjaro.

At the same time, Mounjaro’s price increase from September 2025 means Wegovy is now often the more cost-effective option. NHS access to Mounjaro has begun through primary care, but eligibility criteria are strict, and the rollout is phased over 12 years.

Most people will continue to access these medications privately for the foreseeable future. All three available options, Mounjaro, Wegovy, and Saxenda, require a prescription following a proper medical assessment.

They work best when combined with sustainable changes to eating, exercise, and lifestyle habits. Medication on its own is unlikely to support lasting weight loss.

Research consistently shows that most people regain weight after stopping. The support you receive alongside the medication, and the habits you build during treatment, matter as much as the medication itself.

References

1. Jastreboff, A.M., et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine, 387(3), 205-216.
2. Wharton, S., et al. (2025). Once-weekly semaglutide 7.2 mg in adults with obesity (STEP UP): a randomised, controlled, phase 3b trial. The Lancet Diabetes & Endocrinology, 13(11), 949-963.
3. Aronne, L.J., et al. (2025). Tirzepatide as Compared with Semaglutide for the Treatment of Obesity. New England Journal of Medicine, 393(1), 26-36.
4. Aronne, L.J., et al. (2024). Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial. JAMA, 331(1), 38-48.
5. National Institute for Health and Care Excellence. (2025). Tirzepatide for managing overweight and obesity (TA1026)
6. Medicines and Healthcare products Regulatory Agency. (2025). Drug Safety Update: Tirzepatide (Mounjaro)
7. Wilding, J.P.H., et al. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine, 384(11), 989-1002.
8. Richards, R., et al. (2025). A Remotely Delivered, Semaglutide-Supported Weight Management Program: 12-Month Outcomes. JMIR Formative Research, 9(1), e72577.
9. Lincoff, A.M., et al. (2023). Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes. New England Journal of Medicine, 389(24), 2221-2232.
10. Pi-Sunyer, X., et al. (2015). A Randomized, Controlled Trial of 3.0 mg of Liraglutide in Weight Management. New England Journal of Medicine, 373(1), 11-22.
11. National Institute for Health and Care Excellence. (2020). Liraglutide for managing overweight and obesity (TA664)
12. West, S., et al. (2026). Weight regain following the cessation of medication for weight management: a systematic review and meta-analysis. BMJ, 392, e085304.
13. Wilding, J.P.H., et al. (2022). Weight regain and cardiometabolic effects after withdrawal of semaglutide. Diabetes, Obesity and Metabolism, 24(8), 1553-1564.
14. Eli Lilly and Company. (2025). Lilly’s triple agonist, retatrutide, delivered weight loss of up to an average of 71.2 lbs. Press release, 11 December 2025.