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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NHS Weight Loss Services and Prescription Medication in the UK
The NHS offers weight management services across England, Scotland, Wales, and Northern Ireland, with prescription weight loss medication now available for eligible adults. If you're overweight or living with obesity, your GP can assess you for NHS support, including access to specialist services and prescription treatments like Mounjaro and Wegovy. This guide explains what's available, who qualifies, and how to get started on your weight management journey.
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.
UK-Licensed Prescription Weight Loss Medications
Three prescription medications are now licensed in the UK for weight management: Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist with clinical trial data showing average weight loss of 15–21% of body weight; Wegovy (semaglutide), a GLP-1 injection with evidence of approximately 15% average weight loss; and Saxenda (liraglutide), a daily GLP-1 injection option. All three are prescription-only medicines requiring clinical assessment before being prescribed.
Eligibility typically includes adults with a BMI of 30 kg/m² or above, or BMI 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply due to higher health risks at lower weights. Use our free BMI calculator above to check your starting point, and our GLP-1 weight loss calculator to explore potential outcomes with different medication 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.
Accessing Weight Loss Services: NHS vs Private Routes
NHS access: Your GP can refer you to tier 3 specialist weight management services, where a multidisciplinary team assesses you for prescription medication. Availability and waiting times vary significantly by region—some areas have substantial waiting lists. Private access: You can consult with a UK-licensed prescriber online for clinical assessment, and if suitable, receive a prescription dispensed by a registered pharmacy, without an NHS referral. Both routes require the same clinical eligibility criteria. Speak with your GP about what's available in your area, or explore private options if you wish to access treatment more quickly. Either way, prescription weight loss medication works best alongside reduced-calorie diet, increased physical activity, and behaviour change support.
- 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 NHS weight loss services and private prescription weight loss?
NHS services are free but often involve waiting lists and regional availability differences. Private services are faster but involve payment. Both require the same prescription and clinical assessment. Your GP can advise on NHS options in your area; private services are available through online prescribing.
Am I eligible for NHS weight loss medication?
Generally, you're eligible if you have a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure. Eligibility is assessed individually by your GP or specialist. Use our free BMI calculator to check your starting BMI and speak with your GP about your options.
How much weight can I expect to lose with Mounjaro or Wegovy?
Clinical trials show average weight loss of 15–21% of body weight with Mounjaro and approximately 15% with Wegovy, achieved alongside diet and physical activity changes. Individual results vary significantly. Our GLP-1 weight loss calculator can help you explore potential projections, though actual outcomes depend on your personal circumstances.
How long do I need to take weight loss medication?
Weight loss medications work while you're taking them. Some people continue long-term; others use them for a defined period. Stopping medication may result in gradual weight regain if lifestyle changes aren't sustained. Your prescriber will discuss the right approach for you during your clinical assessment.
Where can I find my local NHS weight management service?
Search "tier 3 weight management services [your region]" online, or ask your GP for a referral. Availability varies by local integrated care board (ICB). If you're struggling to access NHS services, your GP can discuss private options with you as an alternative pathway.
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.