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
NHS Weight Loss Pills UK — What You Need to Know
Weight loss pills are available in the UK through both NHS specialist services and private prescribing, though options are limited compared to other countries. The main prescription weight loss medications available in the UK are GLP-1 receptor agonists like Wegovy (semaglutide) and Mounjaro (tirzepatide), alongside older medications like Saxenda. Access through the NHS involves referral to specialist weight management services, while private prescription is available through online clinics. Understanding your options helps you make an informed decision about weight management in the UK.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 NHS Weight Loss Medication Works
GLP-1 receptor agonists (including Wegovy and Mounjaro) are the main prescription weight loss medications available in the UK. These work by activating natural hormones that regulate appetite and blood sugar. They signal to your brain that you're fuller after eating less, reduce food cravings, and slow how quickly food leaves your stomach.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection; clinical trials showed average weight loss of around 15% body weight over 68 weeks alongside diet and exercise
- Mounjaro (tirzepatide) — a once-weekly dual GIP and GLP-1 injection; SURMOUNT trials showed average weight loss of 15–21% body weight depending on dose
- Saxenda (liraglutide) — a daily GLP-1 injection; available but less commonly prescribed than once-weekly options
All are prescription-only medications requiring clinical assessment before prescription. Individual results vary significantly, and these medications are used alongside reduced-calorie diet and increased physical activity — they are not a standalone solution.
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.
NHS Access vs Private Prescription
NHS access: Weight loss medications are available through specialist tier 3/4 weight management services following GP referral. However, availability varies significantly by region, and waiting lists can be several months to years in many areas. Your GP can refer you if you meet eligibility criteria: BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions like type 2 diabetes, hypertension, or sleep apnoea.
Private access: Available through UK-licensed online prescribing services following clinical assessment. This bypasses NHS waiting lists but involves out-of-pocket costs (typically £129–£320 monthly depending on dose). Calculate your potential weight loss using our free GLP-1 weight loss calculator, and check your BMI with our free BMI calculator to understand your starting point.
- 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 weight loss pills available on the NHS?
Yes, prescription weight loss medications are available through NHS specialist weight management services, but access is regional and waiting lists vary. Your GP can refer you if you meet eligibility criteria (BMI 30+, or 27–29.9 with weight-related health conditions). Availability depends on your local Integrated Care Board and specialist service capacity.
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 weekly), while Ozempic is licensed for type 2 diabetes (doses up to 2 mg). Using Ozempic for weight loss is off-label and not recommended. Wegovy is the correct licensed option for weight management in the UK.
How much weight can you lose with NHS weight loss pills?
Clinical trials show average weight loss of 15–21% of body weight depending on the medication and dose, alongside diet and exercise changes. However, individual results vary significantly — some people lose more, some less. There's no assured amount of weight loss, and results depend on adherence, lifestyle changes, and individual metabolism.
How do I get weight loss pills prescribed on the NHS?
Speak to your GP about your weight and health concerns. If eligible, you'll be referred to a specialist tier 3 weight management service. They'll assess you and may prescribe weight loss medication. The entire process can take weeks to months depending on waiting lists in your area. Private prescription services offer faster access but involve costs.
What are the side effects of NHS weight loss pills?
Most common side effects are nausea, diarrhoea, constipation, and stomach pain — these often improve over time. Less common effects include headache, fatigue, and injection site reactions. Serious side effects are rare but can include pancreatitis or gallbladder problems. Your prescriber will discuss full risk information before prescribing.
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.