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
Pills That Help You Lose Weight in the UK
If you're exploring weight loss methods in the UK, prescription pills and injections can be part of a supported approach when used alongside dietary changes and physical activity. The most effective prescription weight loss treatments available in the UK are GLP-1 receptor agonist medications, though these are typically injections rather than traditional pills. Understanding your options—including how they work, eligibility criteria, and what the evidence shows—helps you make an informed decision with your GP or healthcare provider about what might suit your circumstances.
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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 Do Weight Loss Medications Work?
The most effective weight loss pills and injections available in the UK work by mimicking natural hormones that regulate appetite and fullness. GLP-1 receptor agonists like Wegovy (semaglutide) and Mounjaro (tirzepatide) activate pathways in your brain that signal satiety, reduce cravings, and slow how quickly food leaves your stomach. This means you may feel fuller after eating less, experience fewer urges to snack, and find it easier to stick to a reduced-calorie diet.
The evidence from clinical trials is encouraging: in the STEP-1 trial, participants taking Wegovy alongside a reduced-calorie diet and increased physical activity lost an average of approximately 15% of their body weight over 68 weeks. Results with Mounjaro were even higher, with some participants losing 20% or more of their body weight. However, individual results vary significantly, and these medications work best as part of a comprehensive weight loss programme, not as standalone treatments.
- GLP-1 injections: once-weekly doses, prescription-only
- Effectiveness depends on dose, diet, exercise, and individual factors
- NHS weight management services may offer these after specialist assessment
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 Weight Loss Treatment
To access prescription weight loss treatment in the UK, you'll typically need a BMI of 30 or above, or 27 or above if you have weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds may apply due to higher health risks at lower BMI levels.
You can pursue sustainable weight loss through two main routes: NHS specialist weight management services (tier 3), where waiting lists vary by region, or private prescribing following an online clinical assessment. Your GP can discuss which approach suits you best. Use our free BMI calculator above to check whether you might be eligible, then speak with your healthcare provider about prescription weight loss options alongside lifestyle changes. Remember, safe, sustainable weight loss targets around 0.5–1 kg per week.
- 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 difference between weight loss pills and injections?
Most effective UK-licensed weight loss medications are injections (Wegovy and Mounjaro), not pills. They're given once weekly by subcutaneous injection. Liraglutide (Saxenda) is a daily injection. All require a prescription and clinical assessment before use. Injections allow more consistent dosing and are easier to adjust compared to traditional pills.
Can I get weight loss pills on the NHS?
Yes, through NHS specialist tier 3 weight management services. Your GP can refer you, though waiting times and availability vary significantly by region and integrated care board (ICB). Private prescribing through online consultations is also available without an NHS referral. Ask your GP about what's available in your area.
Are weight loss medications safe?
Prescription weight loss medications like Wegovy and Mounjaro have been extensively studied in clinical trials and are licensed by the MHRA for UK use. Common side effects include nausea and stomach discomfort, which often improve over time. Always discuss your individual health circumstances with a prescriber to ensure it's appropriate for you.
How much weight will I lose with weight loss pills?
Clinical trials show average weight loss of 15–21% of body weight, but individual results vary significantly. Your actual weight loss depends on the medication dose, how closely you follow a reduced-calorie diet, physical activity levels, genetics, and other personal factors. No medication assures specific outcomes.
Do I need to change my diet if I take weight loss pills?
Yes, absolutely. Weight loss medications work best as part of a comprehensive approach that includes a reduced-calorie diet, increased physical activity, and behaviour change support. The medication helps you feel fuller and reduce cravings, making it easier to maintain these changes—but the lifestyle changes are essential for success.
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.