The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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Alternatives to Mounjaro in the UK
If you're considering weight loss medication in the UK but Mounjaro isn't right for you, several prescription alternatives are available through both NHS specialist services and private prescribing. The main alternative to tirzepatide is Wegovy (semaglutide), a GLP-1 injection also licensed for weight management. Saxenda, a daily GLP-1 injection, is another option. This guide explains what these alternatives are, how they work, NHS eligibility criteria, and how to access them through tier 3 services or private prescription routes in the UK.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
NHS-Licensed Weight Loss Alternatives to Mounjaro
Three prescription weight loss medications are currently licensed for use in the UK:
- Wegovy (semaglutide) — a once-weekly GLP-1 injection, similar to Mounjaro but using a single hormone mechanism rather than Mounjaro's dual GIP/GLP-1 action. Clinical trials showed average weight loss of around 15% body weight at maximum dose.
- Saxenda (liraglutide) — a daily GLP-1 injection with a longer track record in the UK. Requires daily dosing rather than weekly, and average weight loss is typically 5–10% body weight.
- Lifestyle modification programmes — NHS tier 3 weight management services provide structured dietary support, physical activity planning, and behavioural therapy, often as first-line treatment before medication is considered.
All three prescription medications require a clinical assessment to confirm eligibility. A Mounjaro kwikpen prescription means you've been assessed for weight management medication — your GP or specialist can discuss which alternative might suit you better based on your health profile, injection preference, and previous response to similar drugs.
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
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Accessing Alternatives Through NHS Tier 3 Services
In the UK, prescription weight loss medications including Wegovy and Saxenda are accessed through NHS specialist tier 3 weight management services, not standard GP prescription. Access varies significantly by region — some areas have established programmes with reasonable waiting times, while others have substantial delays of many months.
Your GP can refer you to your local tier 3 service, where a multidisciplinary team (usually including a dietitian, psychologist, and specialist nurse) will assess your suitability for medication. They consider your BMI, weight-related health conditions, previous weight loss attempts, and contraindications. If Mounjaro isn't suitable (due to cost, side effects, or clinical factors), the same team can prescribe Wegovy or Saxenda depending on NICE guidance and local formulary decisions. Many areas prioritise Wegovy due to NICE approval and cost-effectiveness data from STEP trials.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
What's the main difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whilst Wegovy (semaglutide) is a GLP-1 agonist only. This means Mounjaro activates two hormone pathways, and clinical trials showed slightly higher average weight loss (~20% vs ~15%). However, both require prescription and clinical assessment. Individual results vary significantly.
Can I switch from Mounjaro to Wegovy on the NHS?
Yes, you can discuss switching with your NHS tier 3 specialist if Mounjaro isn't working well or causing side effects you can't tolerate. There's no official conversion chart — your prescriber will reassess your dose. Switching typically requires stopping Mounjaro for a short period before starting Wegovy, depending on clinical guidance.
Is Saxenda still available on the NHS?
Saxenda (liraglutide) is licensed and available in the UK but is less commonly prescribed than Wegovy in NHS tier 3 services. NICE recommends considering Saxenda, but many trusts prioritise Wegovy based on cost-effectiveness data. Saxenda requires daily injections, whereas Wegovy is once-weekly, which influences NHS prescribing decisions.
How long is the NHS waiting list for weight loss medication?
Waiting times vary widely by region and local ICB. Some areas offer appointments within weeks; others have waiting lists of 6–18 months or longer. Contact your local tier 3 weight management service to ask about current waiting times. Private prescribing offers faster access but involves out-of-pocket costs.
Are there other weight loss alternatives besides injections?
Yes. NHS tier 3 services offer structured dietary programmes, very low calorie diets (under medical supervision), physical activity support, and behavioural therapy. For severe obesity, bariatric surgery is an option in tier 4 services. Use our free BMI calculator to check your eligibility for different NHS weight management interventions.
Ready to take control of your weight loss journey?
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