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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MHRA-Approved Weight Loss Medications in the UK
The MHRA (Medicines and Healthcare products Regulatory Agency) has approved several prescription weight loss medications for use in the UK. These are prescription-only medicines that may help support weight management when used alongside a reduced-calorie diet and increased physical activity. Understanding which medications are MHRA-approved, how they work, and whether you might be eligible is an important first step in exploring prescription weight loss options. This guide covers the main MHRA-approved weight loss treatments available in the UK and how they fit into your overall weight management uk journey.
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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.
MHRA-Approved Weight Loss Medications Available in the UK
The MHRA has approved three main GLP-1 and GIP receptor agonist medications specifically licensed for weight management in UK adults:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, once-weekly injection. In clinical trials, participants lost an average of 15–21% of body weight over 72 weeks, though individual results vary significantly.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, once-weekly injection. Clinical trial data showed an average weight loss of approximately 15% of body weight, alongside reduced-calorie diet and increased physical activity.
- Saxenda (liraglutide) — a GLP-1 receptor agonist, once-daily injection. Approved for long-term weight management in eligible adults.
All three are prescription-only medicines that require a clinical assessment before being prescribed. They work by helping regulate appetite, reducing food cravings, and supporting the feeling of fullness after smaller meals. These medications are typically used as part of a comprehensive weight management programme, not as a standalone treatment.
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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.
Free Weight Loss Tools & Guides
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Eligibility and How to Access MHRA-Approved Weight Loss Treatment
To be eligible for prescription weight loss medication in the UK, you generally need a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² if you have weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply.
You can access MHRA-approved weight loss medication nhs through specialist tier 3 weight management services (referral from your GP), though NHS availability varies by region and waiting lists can be lengthy. Alternatively, prescription weight loss uk is available through private online prescribing services following a clinical assessment with a UK-licensed prescriber. Use our free BMI calculator above to check your BMI, and our GLP-1 weight loss calculator to estimate potential outcomes at different doses.
- 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 does MHRA approval mean for weight loss medications?
MHRA approval means the medication has been rigorously tested for safety and effectiveness and is licensed for use in the UK. All MHRA-approved weight loss medications must be prescribed by a UK-licensed prescriber following a clinical assessment. This ensures they are appropriate for your individual health circumstances before you start treatment.
Are MHRA-approved weight loss injections safe?
Yes, MHRA-approved medications have undergone extensive clinical trials and safety monitoring. However, all medications can cause side effects. Common side effects include nausea, diarrhoea, and stomach discomfort, which often reduce over time. Serious side effects are rare but can occur. Your prescriber will discuss potential risks and benefits with you during your assessment.
Can I get MHRA-approved weight loss medication through the NHS?
Yes, MHRA-approved medications are available through NHS specialist weight management services (tier 3). Access requires a referral from your GP and assessment by a specialist team. Availability and waiting times vary significantly by region. You can also access these medications privately through online prescribing services without an NHS referral.
How does Mounjaro differ from Wegovy for weight loss?
Both are MHRA-approved, but Mounjaro is a dual GIP and GLP-1 agonist while Wegovy is a GLP-1 agonist alone. Clinical trials suggest Mounjaro may produce slightly higher average weight loss (15–21% versus approximately 15%), but individual results vary considerably. Your prescriber will determine which is more suitable for you based on your health profile.
What is the difference between Wegovy and Ozempic?
Both contain semaglutide, but Ozempic is approved for type 2 diabetes management, not weight loss. Wegovy is the MHRA-licensed version specifically approved for weight management. Using Ozempic for weight loss would be off-label. Always use the correct, licensed medication prescribed by your healthcare professional.
Ready to take control of your weight loss journey?
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