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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Prescription Weight Loss Pills in the UK
Prescription weight loss pills are available in the UK for adults who meet specific eligibility criteria, though they're not the first option for everyone. The main prescription medications licensed for weight management in the UK are GLP-1 receptor agonist injections like Wegovy (semaglutide) and Mounjaro (tirzepatide), not traditional pills. These are used alongside lifestyle changes—diet and physical activity—rather than instead of them. Access through the NHS varies significantly by region, while private prescribing is also available. Understanding what these medications are, how they work, and whether you might be eligible is the first step toward making an informed decision with your GP.
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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.
How Prescription Weight Loss Medications Work in the UK
The main prescription weight loss medications available in the UK are GLP-1 receptor agonists, which are injections rather than pills. Wegovy (semaglutide) and Mounjaro (tirzepatide) both work by mimicking natural hormones that regulate appetite and blood sugar. In clinical trials, Wegovy helped participants lose an average of 14.9% of their body weight over 68 weeks, while Mounjaro showed weight loss of approximately 15–21% body weight depending on dose. These medications slow gastric emptying so you feel fuller after eating smaller meals and reduce cravings. They're prescribed alongside a reduced-calorie diet and increased physical activity—not as a standalone solution. Both are prescription-only medicines requiring clinical assessment before being dispensed. Individual results vary significantly, and not everyone experiences the same level of weight loss.
Try our GLP-1 weight loss calculator to estimate potential weight loss at different doses, and use our BMI calculator to check whether you might meet eligibility criteria.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
UK Eligibility and How to Access Prescription Weight Loss Treatment
Eligibility for prescription weight loss medication in the UK depends on BMI and health conditions. Adults with a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² with weight-related conditions like type 2 diabetes, high blood pressure, or sleep apnoea, may qualify. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds apply (from BMI 27.5 or above).
NHS access is through specialist tier 3 weight management services—your GP can refer you, though waiting times vary widely by region. Private prescribing is available through online consultations with UK-licensed prescribers; prescriptions are then dispensed by GPhC-registered pharmacies. Either route requires a clinical assessment confirming the medication is appropriate for your individual health. Track your progress once you've started treatment with our free progress tracker.
- 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.
Are there actual weight loss pills available on prescription in the UK?
Most prescription weight loss medications available in the UK are injections, not pills. Wegovy and Mounjaro are the main options, both given once weekly. Saxenda (liraglutide) is available as a daily injection. These are GLP-1 receptor agonists or dual GIP/GLP-1 agonists. Traditional weight loss pills are not commonly prescribed in the UK. All require a prescription and clinical assessment.
What's the difference between Wegovy and Mounjaro?
Wegovy (semaglutide) is a GLP-1 agonist with a maximum dose of 2.4 mg weekly. Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist with a maximum dose of 15 mg weekly. In clinical trials, Mounjaro showed slightly higher average weight loss (15–21%) compared to Wegovy (14.9%), though individual results vary. Both are prescription-only and require clinical assessment.
Can I get prescription weight loss medication on the NHS?
Yes, but access varies by region. GLP-1 medications are available through NHS specialist weight management services (tier 3). Your GP can refer you, though waiting lists can be lengthy. Alternatively, private online prescribing is available without NHS referral. Either route requires a clinical assessment by a UK-licensed prescriber to confirm suitability.
What's the difference between Wegovy and Ozempic?
Both contain semaglutide, but Ozempic is licensed for type 2 diabetes (doses up to 2 mg) and is not approved for weight loss in the UK. Wegovy is the licensed weight management version (doses up to 2.4 mg). Using Ozempic for weight loss would be off-label. Always ensure your prescription specifies Wegovy if weight loss is your goal.
How much weight can I expect to lose on prescription weight loss medication?
Clinical trials show average weight loss of 14.9–21% body weight depending on the medication and dose. However, individual results vary significantly—some people lose more, some less. Weight loss depends on medication, dose, adherence, diet, physical activity, and individual metabolism. Results are not assured. Always discuss realistic expectations with your prescriber.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.