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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Slimming Pill Options in the UK
A slimming pill is just one option for sustainable weight loss in the UK — but it's rarely the first step. The NHS recommends a structured approach starting with lifestyle changes, then progressing to specialist support if needed. Whether you're looking at free NHS weight management or prescription medication, understanding all your options helps you make an informed choice with your GP. This guide covers the full range of weight loss methods available, from self-help to prescription options, to help you find the right approach for your health goals.
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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: From Lifestyle to Prescription Medication
The UK uses a four-tier weight management pathway recognised by the NHS. Tier 1 (self-help) includes the NHS Weight Loss Plan, free apps, and community programmes — this is where most people start. Tier 2 (primary care support) offers GP-led lifestyle interventions and behaviour change coaching, available through your GP surgery. Tier 3 (specialist services) provides multidisciplinary weight management through NHS specialist teams — here, prescription weight loss medications like Mounjaro and Wegovy may be considered if lifestyle changes alone aren't sufficient. Tier 4 (bariatric surgery) is reserved for severe obesity with significant health complications.
Prescription weight loss medications are only one tool within this pathway. The NHS prioritises sustainable weight loss through calorie reduction and increased physical activity first. On average, losing 0.5–1 kg per week is considered safe and sustainable. Use our free BMI calculator above to check whether your current weight falls into the overweight or obese range — this helps inform which tier of support may be most appropriate for you.
Private weight loss options exist alongside the NHS pathway. Online prescribing services offer access to GLP-1 medications (such as semaglutide in Wegovy) and GIP/GLP-1 medications (such as tirzepatide in Mounjaro) without NHS referral, following an online clinical assessment with a UK-licensed prescriber.
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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.
Choosing the Right Weight Loss Approach for You
Selecting the best weight loss method depends on several personal factors: your current BMI, any weight-related health conditions (such as type 2 diabetes or high blood pressure), how much weight you want to lose, and your preferences for lifestyle changes versus medication support.
Start by speaking to your GP, who can assess your individual circumstances and recommend the most suitable tier of the NHS pathway. If you're interested in prescription weight loss medication, your GP can refer you to specialist tier 3 services (though NHS waiting lists vary by region) or advise you on private prescribing options. Track your progress using our free progress tracker — consistent monitoring helps you and your healthcare team assess what's working. Remember, sustainable weight loss works best when combined with dietary changes and increased physical activity, regardless of which method you choose.
- 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 is the difference between a slimming pill and a weight loss injection?
Slimming pills typically refer to oral medications for weight loss, though this term is sometimes used loosely. Weight loss injections like Wegovy (semaglutide) and Mounjaro (tirzepatide) are GLP-1 and GIP/GLP-1 receptor agonists — injectable medications given once weekly. Both are prescription-only and work alongside lifestyle changes. Injections currently have stronger clinical evidence for weight loss in the UK.
Can I get a slimming pill on the NHS?
Prescription weight loss medications are available through the NHS, but only via specialist tier 3 weight management services following referral from your GP. Access varies significantly by region and waiting lists can be lengthy. Private online prescribing offers quicker access if you choose to pay privately. Your GP can advise on both routes.
How much weight will I lose with a slimming pill?
Weight loss varies significantly between individuals. Clinical trials for GLP-1 medications show average losses of 14–21% of body weight over several months, alongside dietary changes and exercise. However, some people lose more, others less. Your GP or prescriber can discuss realistic expectations based on your individual health profile.
Is a slimming pill safe long-term?
Prescription weight loss medications are monitored by the MHRA and have safety profiles established through clinical trials. Like all medications, they have potential side effects — nausea and digestive changes are most common. Long-term safety data continues to develop. Always discuss risks and benefits with your GP or prescriber before starting any medication.
What should I try before considering a slimming pill?
The NHS recommends starting with Tier 1 support: use the free NHS Weight Loss Plan, download evidence-based apps, and join community weight management programmes. If this isn't sufficient after several months, speak to your GP about Tier 2 primary care support. Prescription medications are considered after lifestyle interventions have been tried, though a prescriber may recommend them alongside lifestyle changes depending on your circumstances.
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.