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: Prescription Medication Options Available in the UK
If you're looking to lose weight in the UK, the NHS offers multiple support pathways—from digital tools and lifestyle programmes to specialist prescription medications. For eligible adults, weight management options now include licensed prescription injections like Mounjaro and Wegovy alongside traditional support. This guide explains who qualifies, what medications are available through NHS specialist services and private prescribing, and how to start a conversation with your GP about the right approach for your health.
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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.
UK-Licensed Weight Loss Medications: What's Available?
Three prescription-only medications are currently licensed in the UK for weight management in adults. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist administered once weekly—clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks when combined with a reduced-calorie diet and increased physical activity. Wegovy (semaglutide) is a GLP-1 receptor agonist also given once weekly; STEP trial data showed approximately clinically studied weight loss on average at the maximum dose. Saxenda (liraglutide) is a daily GLP-1 injection, though less commonly prescribed now. All three are prescription-only and require a clinical assessment before being prescribed. Individual results vary significantly based on adherence, diet, exercise, and personal metabolism. Use our GLP-1 weight loss calculator to estimate potential outcomes at different doses, and check your BMI using our free BMI calculator to understand your starting point.
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: How to Get Started
The NHS route involves referral to a specialist tier 3 weight management service from your GP, though regional availability varies significantly—waiting lists can extend many months in some areas. Alternatively, licensed private prescribers offer online consultations and prescription through regulated pharmacies without an NHS referral. To explore NHS options, speak with your GP about whether you meet eligibility criteria: BMI of 30 or above, or BMI 27–29.9 with a weight-related health condition like type 2 diabetes, hypertension, or sleep apnoea. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower thresholds due to increased health risks. Your GP can assess your individual situation and discuss both NHS pathways and private prescribing options. Track your weight journey using our free progress tracker alongside any weight loss medication.
- 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 Mounjaro and Wegovy for weight loss?
Both are once-weekly injections for weight management. Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates GLP-1 only. Clinical trials showed Mounjaro produced slightly higher average weight loss (15–21% vs 15%), though individual results vary. Both require prescription and clinical assessment.
Am I eligible for weight loss medication on the NHS?
You may be eligible if you have a BMI of 30 or above, or BMI 27–29.9 with a weight-related health condition such as type 2 diabetes, hypertension, sleep apnoea, or cardiovascular disease. Lower BMI thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Your GP can assess your individual eligibility.
How long does it take to see weight loss results with these medications?
Most people begin to notice changes within 4–8 weeks of starting, though results vary. Clinical trials ran for 68–72 weeks to measure full outcomes. Weight loss is ongoing during treatment and typically plateaus after 12–16 weeks at a stable dose. Results depend on adherence, diet, exercise, and individual metabolism.
Can I get weight loss injections privately if I don't qualify for the NHS?
Yes. Licensed private prescribers offer online consultations and prescription through regulated pharmacies. Private access does not require NHS referral, though you still need a prescription following clinical assessment. Costs vary by dose and provider, typically ranging from £129–£320 monthly.
What should I discuss with my GP about weight loss medication?
Ask about NHS specialist referral pathways, eligibility criteria based on your BMI and health conditions, potential side effects, suitability alongside any existing medications, and whether private prescribing options might be faster. Your GP can help you weigh NHS and private routes based on your individual health and 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.