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 Make You Lose Weight — What Works in the UK
Several prescription-only weight loss pills are available in the UK, though they work differently and are prescribed based on individual health assessment. The most commonly prescribed weight loss medications in the UK are GLP-1 receptor agonists, which help regulate appetite and support sustainable weight loss. These aren't quick-fix solutions — they work best alongside a reduced-calorie diet and increased physical activity. Understanding how these medications work, who can take them, and what to expect is essential before exploring prescription weight loss options.
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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 Prescription Weight Loss Pills Work in the UK
Weight loss pills prescribed in the UK are prescription-only medicines that work by affecting how your body regulates appetite and blood sugar. The main types available are GLP-1 receptor agonists, which include Wegovy (semaglutide) and Saxenda (liraglutide), and dual GIP/GLP-1 agonists like Mounjaro (tirzepatide).
These medications mimic natural hormones your gut produces after eating. They signal your brain that you're full, slow how quickly food leaves your stomach, and reduce cravings — helping you eat less without feeling deprived. In clinical trials, GLP-1 weight loss methods showed average weight loss of 14–15% of body weight, though individual results vary significantly. Importantly, these pills only work effectively when combined with sustainable lifestyle changes including a reduced-calorie diet and regular physical activity.
- Wegovy (semaglutide) — once-weekly injection, average clinically studied weight loss
- Mounjaro (tirzepatide) — once-weekly injection, average 15–clinically studied weight loss
- Saxenda (liraglutide) — daily injection, average 5–clinically studied weight loss
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.
Who Can Get Weight Loss Medication in the UK
NHS weight management prescription eligibility in the UK requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or heart disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply due to higher health risks at lower weights. Weight loss pills are prescription-only and require a clinical assessment from a GP or licensed prescriber to confirm they're safe and appropriate for you.
Private access is available without NHS referral through GPhC-registered online pharmacies following an online consultation. Whichever route you choose, a qualified prescriber will assess your individual circumstances. Use our GLP-1 weight loss calculator to explore potential outcomes, and check your BMI using our free calculator to understand your starting point.
Weight loss is never assured, and results depend on adherence to medication, diet, and exercise. The NHS recommends losing 0.5–1 kg per week for sustainable results. These pills work best when you're committed to lifestyle changes — they're a tool to support you, not a replacement for healthy eating and movement. Common side effects include nausea, diarrhoea, and reduced appetite, which usually improve over time. Track your progress with our free progress tracker to monitor changes beyond just weight, including energy levels and how your clothes fit.
- 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 Wegovy and Ozempic?
Both contain semaglutide, but Wegovy is specifically licensed for weight management in the UK at doses up to 2.4 mg. Ozempic is approved for type 2 diabetes (up to 2 mg) and is not licensed for weight loss. Using Ozempic for weight loss is off-label. Always use the medication prescribed by your doctor.
Can I get weight loss pills on the NHS?
Yes, through NHS specialist tier 3 weight management services. You'll need a GP referral and will be assessed for eligibility (BMI 30+ or 27+ with health conditions). Availability varies significantly by region, and waiting lists can be long. Private access is available without NHS referral through registered pharmacies.
How quickly will I lose weight on these pills?
Clinical trials show average weight loss of 14–21% of body weight over several months, but individual results vary. The NHS recommends losing 0.5–1 kg per week for sustainable results. Weight loss depends on your starting weight, diet, exercise, and how your body responds to medication.
Are weight loss pills safe?
Prescription weight loss medications are safe for most adults when prescribed by a qualified healthcare provider following clinical assessment. Common side effects include nausea and diarrhoea, usually temporary. Serious side effects are rare but can include pancreatitis or gallbladder issues. Always discuss risks with your prescriber.
Will I regain weight if I stop taking weight loss medication?
Weight regain is possible after stopping, particularly without continued lifestyle changes. These medications are most effective as part of a sustained approach including diet and exercise. Some people continue medication longer-term to maintain results. Discuss long-term plans with your prescriber.
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.