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
New Weight Loss Pill — What You Need to Know
New weight loss pills available in the UK are prescription-only medications that work differently from traditional diet pills. The most recent licensed options are GLP-1 receptor agonist injections, including Wegovy (semaglutide), which have shown significant results in clinical trials. Unlike older weight loss pills, these medications help regulate appetite and support feeling fuller after smaller meals. Access is through NHS specialist services or private prescribing following a clinical assessment. Weight management in the UK has evolved considerably, with evidence-based medication now recognised as a legitimate treatment option alongside lifestyle changes.
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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.
How New Weight Loss Medications Work
New weight loss pills approved in the UK use a mechanism called GLP-1 receptor agonism. GLP-1 (glucagon-like peptide-1) is a natural hormone your gut produces after eating. These medications mimic and enhance this hormone's effects, signalling to your brain that you're full and reducing food cravings. Unlike older appetite suppressants, GLP-1 medications also slow how quickly food leaves your stomach and help regulate blood sugar.
The most established new option is Wegovy (semaglutide). In the STEP-1 clinical trial, participants taking 2.4 mg achieved an average weight loss of approximately 15% of their body weight over 68 weeks alongside a reduced-calorie diet and increased physical activity. Individual results vary significantly — some people lose more, some less. Wegovy is a once-weekly injection, making it convenient for ongoing use. These are prescription-only medicines requiring a clinical assessment before being prescribed.
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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
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Eligibility and How to Access in the UK
In the UK, new weight loss pills are available if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or heart disease. Use our free BMI calculator above to check your current BMI instantly.
NHS access: Referral to a tier 3 specialist weight management service, though waiting times vary significantly by region. Private access: Available through UK-licensed prescribers following an online clinical assessment, with prescription dispensed by a GPhC-registered pharmacy. Private prescriptions typically cost £129–£320 per month depending on dose. Your GP can discuss which route is suitable for you and refer you to NHS services if eligible in your area.
- 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 new weight loss pills safe?
Prescription weight loss medications like Wegovy undergo rigorous clinical trials and regulatory approval. Common side effects include nausea, diarrhoea, and constipation. Serious side effects are rare but can include pancreatitis. Any new medication carries risks — your prescriber will assess whether it's appropriate for your individual health. Always report side effects to your healthcare provider.
How quickly will I lose weight on a new weight loss pill?
Results vary significantly between individuals. Clinical trials show average weight loss of around 15% of body weight over 68 weeks when combined with reduced-calorie diet and increased physical activity. The NHS recommends losing no more than 0.5–1 kg per week for sustainable results. Use our GLP-1 weight loss calculator above to estimate potential weight loss at different doses.
What's the difference between Wegovy and Ozempic?
Both contain semaglutide, but Wegovy is licensed specifically for weight management (doses up to 2.4 mg), while Ozempic is licensed for type 2 diabetes (doses up to 2 mg). Ozempic is not licensed for weight loss in the UK — using it for weight loss is off-label. Wegovy is the approved weight management version of semaglutide.
Do I need a prescription for new weight loss pills?
Yes. All new weight loss medications approved in the UK are prescription-only. You cannot buy them over the counter. A UK-licensed prescriber must assess your medical history, BMI, and health conditions before prescribing. This can be done through NHS specialist services or private online consultations with registered prescribers.
Will I regain weight when I stop taking weight loss medication?
Weight regain is common after stopping GLP-1 medication — this is why these medications are intended as ongoing treatment, not short-term use. Research suggests maintaining weight loss requires continued medication or permanent lifestyle changes. Your prescriber will discuss long-term plans with you and support sustainable weight management through diet and exercise.
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.