The best weight-loss injections in 2025

Jump to: Comparison at a glance | 1. Tirzepatide (Mounjaro) | 2. Semaglutide (Wegovy) | 3. Liraglutide (Saxenda) | NHS vs private access | Side effects comparison | Cost analysis | How to choose | Future medications | Frequently asked questions | Take home message

Based on data from randomised controlled trials, the most effective weight-loss injection available in the UK in 2025 is tirzepatide (Mounjaro), which supports an average weight loss of 20-25% of starting body weight after 72 weeks¹.

While Mounjaro leads in effectiveness, choosing the right weight-loss injection depends on multiple factors, including your health conditions, budget, NHS eligibility, and how your body responds to different medications.

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

Most people in the UK access these medications through private prescriptions costing ~£150-400 a month, as NHS availability remains extremely limited despite NICE approval for certain medications.

Weight-loss injections: comparison

Understanding the key differences between available weight-loss injections helps you make an informed decision with your healthcare provider.

Feature	Mounjaro	Wegovy	Saxenda
Drug	Tirzepatide	Semaglutide 2.4 mg	Liraglutide
Average weight loss	20-25%	15-17%	5-7%
Injection frequency	Weekly	Weekly	Daily
NHS availability	Very limited (2025 rollout)	Limited specialist services	Tier 3 services only
Private cost/month	~£200-400	~£150-250	~£150-300
Time to see results	4-8 weeks	4-8 weeks	8-12 weeks
Main side effects	Nausea, diarrhoea	Nausea, constipation	Nausea, headaches

1. Tirzepatide (Mounjaro) – Most effective for weight loss

Tirzepatide, marketed as Mounjaro in the UK, represents the newest generation of weight-loss medications with the highest efficacy shown in clinical trials.

How Mounjaro works

Unlike other weight-loss injections, Mounjaro mimics GLP-1 and GIP hormones, creating a dual function that enhances weight loss².

This dual action reduces appetite, slows gastric emptying, and improves how your body processes sugars and fats.

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

Clinical evidence for weight loss

The SURMOUNT-1 trial demonstrated that participants without diabetes lost an average of 20.9% of body weight at the 15 mg dose after 72 weeks¹.

Remarkably, 91% of participants achieved at least 5% weight loss, with 57% achieving 20% or greater weight reduction.

Follow-up data shows weight loss is maintained at 88 weeks, suggesting sustained effectiveness with continued use³.

Who can take Mounjaro?

NICE has approved Mounjaro for adults with a BMI of 30 or above, or BMI 27 with weight-related health conditions⁴.

However, you cannot 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, severe gastrointestinal disease, or diabetic retinopathy need careful assessment before starting.

Accessing Mounjaro in the UK

Despite NICE approval, NHS access remains extremely limited, with most people opting to purchase services through private weight loss providers.

Private prescriptions typically cost ~£200-400 monthly depending on dose, with additional consultation and monitoring fees.

The medication requires proper medical assessment and ongoing monitoring, making unregulated online purchases dangerous and illegal.

2. Semaglutide (Wegovy) – Established and effective

Semaglutide 2.4 mg, branded as Wegovy, was the first weekly GLP-1 medication specifically approved for weight loss in the UK.

How Wegovy differs from Ozempic

While both contain semaglutide, Wegovy uses a higher dose (2.4 mg) specifically optimised for weight loss compared to Ozempic’s maximum 1 mg dose for type 2 diabetes.

The weight-loss dose demonstrated superior results in head-to-head comparisons, though Ozempic is no longer prescribed off-label for weight loss in the UK.

Wegovy follows a 16-week dose escalation schedule, starting at 0.25 mg and gradually increasing to minimise side effects.

Weight loss outcomes

The STEP 1 trial showed participants achieved an average 14.9% weight loss over 68 weeks when combined with lifestyle interventions⁵.

In real-world UK settings, Second Nature’s data show participants achieving a 19% (~20kg) weight loss with comprehensive support.

Approximately 86% of people achieve clinically meaningful weight loss of 5% or more on Wegovy.

Advantages of Wegovy

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

The medication shows particular benefits for cardiovascular health, reducing major cardiac events by 20% in people with existing heart disease⁷.

Many users report improved energy levels, reduced joint pain, and weight loss.

3. Liraglutide (Saxenda) – The daily injection option

Saxenda, containing liraglutide 3.0 mg, remains available as a daily injection option, though its popularity has declined with weekly alternatives available.

Clinical effectiveness

The SCALE trials demonstrated average weight loss of 5-7% over 56 weeks, modest compared to newer medications⁸.

However, 63% of participants achieved at least 5% weight loss, meeting the threshold for health improvements.

Saxenda demonstrates particular effectiveness in blood sugar control, with 56% of prediabetic participants returning to normal glucose levels.

Daily injection considerations

The daily injection schedule can be challenging to maintain, with studies showing 25% discontinuation rates due to injection burden.

Some people prefer daily dosing for the flexibility to stop quickly if side effects occur.

The pen device allows dose adjustments in 0.6 mg increments, offering more granular control than weekly medications.

When Saxenda might be preferred

Saxenda may suit people who have previously not tolerated weekly GLP-1 medications or prefer daily dosing control.

The lower cost compared to newer medications makes it accessible when budget is a primary concern.

Some NHS tier 3 services still primarily offer Saxenda due to established procurement pathways following NICE guidance¹².

 

NHS vs private access to weight-loss injections

Understanding the realities of accessing weight-loss medications in the UK helps set appropriate expectations and plan your approach.

NHS access: Currently limited

Despite NICE approval for Mounjaro⁴, Wegovy¹³, and Saxenda¹², NHS implementation remains extremely limited across the UK in 2025.

Most NHS access requires referral to specialist tier 3 weight management services, with eligibility typically requiring:

• BMI ≥35 with obesity-related conditions (or ≥32.5 for certain ethnic groups)
• Documented previous weight loss attempts
• Commitment to 12-18 month programmes
• Meeting local commissioning criteria

Waiting times for tier 3 services range from 6-24 months, depending on location, with significant regional variations.

Scotland, Wales, and Northern Ireland have different implementation timelines and criteria from England.

Private prescription routes

Private weight management clinics offer immediate access but require careful selection to ensure safety and legitimacy.

Reputable providers include CQC-registered clinics with qualified prescribers who conduct proper medical assessments.

Avoid providers offering prescriptions without proper assessment or those shipping from overseas without UK licensing.

Insurance coverage

Most UK private health insurance explicitly excludes weight-loss medications, considering them lifestyle treatments. However, Second Nature has partnered with Vitality to offer weight-loss medications alongside our weight-loss programme. 

Some employers offer wellness benefits that partially cover weight management programmes but rarely include medication costs.

Always verify coverage before starting treatment, as retroactive claims are typically denied.

Side effects comparison

Understanding potential side effects helps you prepare for treatment and recognise when to seek medical advice.

Common side effects across all GLP-1 medications

Gastrointestinal effects dominate early treatment, typically improving after 4-8 weeks as your body adjusts.

Nausea affects 30-40% of users initially but usually responds well to dietary modifications and slower dose escalation.

Constipation or diarrhoea may alternate, and can be managed through hydration and fibre adjustment.

Fatigue and headaches occur in 10-15% of users, often related to reduced calorie intake rather than the medication itself.

Medication-specific patterns

Side Effect	Mounjaro	Wegovy	Saxenda
Nausea	30%	44%	40%
Diarrhoea	21%	30%	21%
Constipation	17%	24%	19%
Injection site reactions	3%	5%	14%
Discontinuation rate	7%	7%	10%

Serious but rare side effects

Pancreatitis occurs in less than 0.2% of users but requires immediate medical attention for 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, requiring ophthalmology monitoring.

Thyroid C-cell tumours seen in animal studies haven’t been confirmed in humans but remain a theoretical concern.

Cost analysis of weight-loss injections in the UK

Understanding the full financial commitment helps you budget appropriately for weight-loss medication treatment.

Monthly medication costs (private prescriptions)

Prices vary significantly between providers and doses:

• Mounjaro: ~£200-400 a month
• Wegovy: ~£150-250 a month
• Saxenda: ~£150-300 monthly (typically 3 pens needed)

Additional costs include consultation fees (£50-150), blood tests (£50-100), and delivery charges.

Most people require 12-24 months of treatment, making total costs £2,000-8,000 for a full course.

Value considerations

Calculate cost per percentage of weight lost: Mounjaro at £300/month, achieving 20% loss equals £180 per 1% lost annually.

Compare this to other weight management options like commercial programmes (£30-50/month) or bariatric surgery (£8,000-15,000).

Consider health improvement benefits: reduced medication needs for diabetes or blood pressure may offset some costs.

Factor in the high likelihood of weight regain if stopping medication without establishing sustainable habits.

 

How to choose the right weight-loss injection

Selecting the most appropriate medication involves weighing multiple factors with your healthcare provider.

Key decision factors

Effectiveness needs: If you need to lose 20% or more body weight, Mounjaro shows the highest success rates.

Budget constraints: Saxenda or Wegovy may be more accessible if cost is the primary concern.

Injection frequency: Weekly injections (Mounjaro/Wegovy) improve adherence over daily Saxenda for most people.

Side effect tolerance: Previous GLP-1 experience can guide selection, as side effect profiles vary.

Health conditions: Certain conditions may favour specific medications (e.g., Wegovy for heart disease).

Medical considerations

Your doctor will assess contraindications, including thyroid cancer risk, pancreatitis history, and kidney function.

Current medications need review for interactions, particularly insulin or sulfonylureas requiring dose adjustments.

Pregnancy plans preclude all GLP-1 medications, requiring discontinuation 2-3 months before conception.

Mental health history matters, as rapid weight changes can affect mood and require monitoring.

Practical decision framework

1. Confirm BMI eligibility (≥30 or ≥27 with comorbidities)
2. Rule out contraindications through medical assessment
3. Consider the budget for 12-24 months of treatment
4. Choose based on effectiveness needs vs cost tolerance
5. Ensure access to ongoing support beyond medication

Remember that medication alone rarely produces lasting results without addressing underlying habits and behaviours.

Future weight-loss medications in development

Several promising medications in late-stage trials may expand UK treatment options within 2-5 years.

Wegovy 7.2 mg – Higher dose semaglutide

Novo Nordisk has developed a higher 7.2 mg dose of semaglutide, showing impressive results in the STEP UP trial¹¹.

This higher dose achieved 20.7% average weight loss compared to 17.5% with the standard 2.4 mg dose, with one-third of participants losing 25% or more of their body weight.

The European Medicines Agency received the application in July 2025, with UK availability likely by early to mid-2026 following MHRA approval.

Private prescription costs are expected to be ~£250-300 per month, slightly higher than the current 2.4 mg dose.

This positions Wegovy 7.2 mg competitively against Mounjaro, potentially giving patients who plateau on standard Wegovy another option before switching medications.

Retatrutide – The triple agonist

Eli Lilly’s retatrutide activates GLP-1, GIP, and glucagon receptors at the same, a unique triple action.

Phase 2 trials showed an unprecedented 24% average weight loss at 48 weeks, with 100% achieving 5% reduction.

The glucagon component may help preserve muscle mass during weight loss, addressing a key concern.

UK availability likely 2027-2028, pending phase 3 completion and MHRA approval.

Orforglipron – Daily pill option

Pfizer’s oral GLP-1 medication could eliminate injection barriers for needle-phobic patients.

Early data suggest 10-15% weight loss efficacy, less than injectables but potentially more accessible.

Daily dosing allows easier titration and discontinuation if needed.

Expected UK submission 2026-2027 if phase 3 trials confirm safety and efficacy.

Oral semaglutide (Rybelsus) 50 mg

Novo Nordisk is developing a higher-dose version of its existing Rybelsus diabetes medication.

Phase 3 OASIS programme showed 15.1% weight loss, approaching injectable Wegovy efficacy¹⁰.

The convenience of a daily pill with an established semaglutide safety profile appeals to many.

A potential UK launch is scheduled for 2026, although supply constraints may impact availability.

CagriSema combination therapy

Novo Nordisk’s combination of semaglutide with cagrilintide (amylin analogue) targets two pathways.

Early results suggest 15-20% weight loss with potentially fewer gastrointestinal side effects.

The combination approach may help people who plateau on single medications.

The UK timeline is uncertain but likely to be 2027-2029, given the current development stage.

Frequently asked questions

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

Based on clinical trial data, Mounjaro (tirzepatide) shows the highest efficacy with an average weight loss of 20-25% at the maximum dose.

However, ‘most effective’ depends on individual factors, including your response, tolerance to side effects, and ability to maintain treatment financially for 12-24 months.

Can I get weight-loss injections on the NHS?

NHS access remains very limited despite NICE approval.

You typically need a referral to specialist Tier 3 weight management services, which have 6-24 month waiting lists. Eligibility usually requires a BMI ≥35 with health conditions or ≥40 without.

Most people currently access these medications privately.

How much do weight-loss injections cost privately in the UK?

Private prescriptions cost £150-400 monthly, depending on medication and dose. Mounjaro ranges from £200-400, Wegovy £150-250, and Saxenda £150-300.

Budget £2,000-8,000 for a complete 12-24 month treatment course.

What’s the difference between Ozempic and Wegovy?

Both contain semaglutide, but at different doses. Wegovy uses 2.4mg specifically approved for weight loss, while Ozempic maxes at 1mg for diabetes. Ozempic is no longer prescribed off-label for weight loss in the UK.

Wegovy achieves superior weight loss due to the optimised higher dose.

How quickly will I see results from weight-loss injections?

Most people notice appetite reduction within days, but 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. Individual responses vary significantly, with some seeing faster or slower progress.

What happens when I stop taking weight-loss injections?

Research shows most people regain weight after stopping, with studies indicating 50-70% regain within one year without ongoing support.

This is why developing sustainable habits during treatment is crucial. Some people maintain weight loss through lifestyle changes, while others may need long-term medication or cycling approaches.

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

Current safety data supports long-term use with appropriate monitoring. The longest studies span 2-3 years with reassuring safety profiles.

Regular monitoring includes kidney function, gallbladder health, and potential thyroid changes. Most side effects occur early and improve over time. For many people, the long-term cardiovascular benefits may outweigh the risks.

Which injection has the fewest side effects?

Side effect profiles are similar across GLP-1 medications, though individual responses vary. Mounjaro shows slightly lower nausea rates (30%) compared to Wegovy (44%) in trials.

Saxenda’s daily dosing allows for a more gradual adjustment but requires daily injections. Starting with lower doses and slow escalation minimises side effects regardless of medication choice.

Take home message

The best weight-loss injection in the UK depends on your individual circumstances; however, Mounjaro currently leads in effectiveness, with an average weight loss of 20-25%.

All three available options – Mounjaro, Wegovy, and Saxenda – require prescription following proper medical assessment and work best combined with sustainable lifestyle changes.

While NHS access remains limited, private prescriptions offer immediate availability at £150-400 monthly, making the total investment substantial at £2,000-8,000 for complete treatment.

Success with any weight-loss injection depends not just on the medication itself, but on developing habits that support long-term weight maintenance after treatment.

Consider factors beyond just effectiveness: your budget, health conditions, injection frequency preference, and access to supportive programmes all influence the best choice.

Remember that these medications are tools to support weight loss, not magic solutions; they require commitment to dietary changes and increased physical activity for optimal results.

Whatever option you choose, ensure you work with legitimate healthcare providers who offer proper assessment, monitoring, and support throughout your weight-loss journey.

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. Frías, J.P., et al. (2021). Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes. New England Journal of Medicine, 385(6), 503-515.
3. 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.
4. National Institute for Health and Care Excellence. (2023). Tirzepatide for treating type 2 diabetes (TA924)
5. 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.
6. Richards, R., et al. (2025). A Remotely Delivered, Semaglutide-Supported Weight Management Program: 12-Month Outcomes From a Retrospective Service Evaluation. JMIR Formative Research, 9(1), e72577.
7. Lincoff, A.M., et al. (2023). Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes. New England Journal of Medicine, 389(24), 2221-2232.
8. 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.
9. Jastreboff, A.M., et al. (2023). Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine, 389(6), 514-526.
10. Knop, F.K., et al. (2023). Efficacy and safety of oral semaglutide 50 mg taken once per day in adults with overweight or obesity (OASIS 1): a randomised, double-blind, placebo-controlled, phase 3 trial. The Lancet, 402(10403), 705-719.
11. Aronne, L.J., et al. (2025). Efficacy and Safety of Semaglutide 7.2 mg/week: the STEP UP Trial. Diabetes, 74(Supplement 1), 1966-LB.
12. National Institute for Health and Care Excellence. (2020). Liraglutide for managing overweight and obesity (TA664) 
13. National Institute for Health and Care Excellence. (2023). Semaglutide for managing overweight and obesity (TA875)