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
Free tracker included with every download this week
Diet Pills That Are Prescribed in the UK
Prescribed diet pills and weight loss medications are available in the UK through both NHS and private routes, but they're only one part of an effective weight loss strategy. Rather than pills alone, modern prescription weight loss treatment typically involves injectable medications like GLP-1 receptor agonists, combined with dietary changes and physical activity. This guide explores all your options—from free NHS support to specialist services—to help you find the safest, most sustainable approach for your situation.
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Calculate Your BMI Instantly
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.
Weight Loss Options Available in the UK
The UK offers a structured pathway for weight loss support, with most people starting at NHS Tier 1—free resources including the NHS Weight Loss Plan, healthy eating guides, and activity trackers. Tier 2 involves primary care support through your GP, including behaviour change programmes and group weight management sessions available in many areas.
For those who need more intensive support, Tier 3 specialist weight management services offer multidisciplinary care, dietary advice, and sometimes prescription medication including GLP-1 injections like Mounjaro or Wegovy. Tier 4 involves bariatric surgery for severe obesity with significant health complications. Access varies by region—your GP can discuss which tier is appropriate for you. Use our free BMI calculator to understand your starting point, and our GLP-1 weight loss calculator can help estimate potential outcomes if medication is recommended.
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.
Prescription Weight Loss Medications Explained
GLP-1 receptor agonist injections—such as Mounjaro (tirzepatide) and Wegovy (semaglutide)—are the main prescription weight loss medications currently licensed in the UK. These work by reducing appetite, helping you feel fuller after smaller meals, and supporting sustainable weight loss. Clinical trials showed average weight loss of 15–21% with Mounjaro and around 15% with Wegovy, though individual results vary significantly.
Eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure. Prescription weight loss medications are always used alongside lifestyle changes—diet and exercise remain essential. Access through the NHS involves referral to tier 3 services; private options are available through online prescribing following clinical assessment. Costs vary depending on dose and provider.
- 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 oral diet pills available on prescription in the UK?
Most prescription weight loss options in the UK are now injectable GLP-1 medications (Mounjaro and Wegovy) rather than oral pills. An older oral medication called orlistat is available over the counter without prescription, but newer GLP-1 injections are more effective and are the primary prescription option through NHS specialist services and private providers.
Can I get prescribed weight loss medication through my GP?
Your GP can discuss weight loss options with you, but prescription weight loss medications are typically initiated through NHS Tier 3 specialist weight management services, accessed via GP referral. Waiting times vary significantly by region. Private prescribing is also available through UK-licensed online prescribers following a clinical consultation.
How do prescription weight loss medications compare to lifestyle changes alone?
Evidence suggests prescription medications are most effective when combined with reduced-calorie diet and increased physical activity. On their own, they're less effective than the combination. The NHS recommends losing 0.5–1 kg per week for sustainable results—whether using medication or lifestyle changes alone.
What is sustainable weight loss, and why does it matter?
Sustainable weight loss typically means losing 0.5–1 kg per week, achieved through a calorie deficit of around 500 kcal per day. This pace helps preserve muscle mass and is more likely to be maintained long-term compared to gradual weight management. Even losing 5–10% of your body weight brings meaningful health benefits.
How do I know which weight loss approach is right for me?
Start by discussing your situation with your GP—they can assess your BMI, any weight-related health conditions, previous weight loss attempts, and personal preferences. Use our free BMI calculator to understand your baseline. Your GP can then refer you to NHS Tier 2 or Tier 3 services, or discuss private options. The right approach depends on your individual circumstances, not a one-size-fits-all solution.
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.