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
Best Diet Pills 2025 — Your UK Weight Loss Options
Looking for the best diet pills available in the UK? Weight loss in 2025 involves far more than just pills — it's about finding the right approach for your individual needs. The NHS offers a structured pathway ranging from free lifestyle support through to specialist prescription medication and surgery. This guide explores all options available to you, helping you understand what's realistic, safe, and effective for sustainable weight loss.
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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 NHS recommends a four-tier weight management pathway that matches your needs and circumstances:
- Tier 1: Self-help using digital tools, community programmes, and NHS resources — completely free
- Tier 2: Primary care-based support through your GP, including behaviour change programmes and digital coaching
- Tier 3: Specialist multidisciplinary weight management services where prescription weight loss medications are assessed and prescribed, including GLP-1 injections like Mounjaro and Wegovy
- Tier 4: Bariatric (weight loss) surgery for severe obesity with significant health complications
Beyond medication, nhs weight management emphasises lifestyle changes: reduced-calorie diet, increased physical activity, and behaviour modification. Evidence shows that combining dietary changes with increased exercise produces the most sustainable results. For many people, lose weight safely means starting with tier 1 or 2 support before considering prescription options.
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.
How to Choose the Right Weight Loss Approach
Selecting the best approach depends on several factors: your current BMI, any weight-related health conditions (like type 2 diabetes or high blood pressure), previous weight loss attempts, your lifestyle, and your preferences. Use our free BMI calculator above to determine where you sit on the NHS weight categories — this helps guide which tier may be appropriate for you.
For sustainable weight loss, most people benefit from starting with lifestyle changes: a calorie deficit of around 500 kcal per day typically results in losing approximately 0.5–1 kg per week. If lifestyle changes alone aren't sufficient after 3–6 months, your GP can discuss whether prescription weight loss medication might help. Our GLP-1 weight loss calculator can help you explore potential outcomes with medication. Always have this conversation with your GP — they'll assess what's safe and appropriate for you individually.
- 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 are the best diet pills available on the NHS in 2025?
The NHS prescribes three GLP-1 medications for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). All are prescription-only and require clinical assessment. Access is through tier 3 specialist weight management services. Availability and waiting times vary significantly by region. Your GP can refer you to your local service.
Are diet pills alone enough for weight loss?
No. All prescription weight loss medications work best alongside reduced-calorie diet and increased physical activity. Clinical trials showed that medication combined with lifestyle changes produces the best results. Medication supports these efforts — it's not a replacement for them.
How do I know if I'm eligible for prescription weight loss medication?
You may be eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure. South Asian, Chinese, Black African, or Black Caribbean adults may have slightly lower thresholds. Your GP or a prescriber can assess your individual eligibility.
What's the difference between NHS and private weight loss medication access?
NHS access is through specialist tier 3 services (often with waiting lists). Private access is through online consultations with UK-licensed prescribers, available without NHS referral, but involves a cost. Both require a clinical assessment — medication is prescription-only in either route.
How much weight can I realistically lose with diet pills?
Clinical trials showed that GLP-1 medications help participants lose an average of 15–21% of their body weight over 68–72 weeks, alongside diet and exercise. Individual results vary significantly. Your GP or prescriber can discuss realistic expectations for your situation.
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.