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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MS and Weight Loss: Medication Options Available in the UK
If you're living with multiple sclerosis and struggling with weight management, prescription medication options are now available in the UK to support sustainable weight loss. Unlike over-the-counter supplements, prescription weight management medications work through clinically proven mechanisms and are available through both NHS specialist services and private prescribing. This guide explores your options, eligibility criteria, and how to access support through your GP or a licensed prescriber.
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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 Prescription Weight Loss Medications
Three prescription-only medications are currently licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). All three are GLP-1 receptor agonists (Mounjaro is a dual GIP/GLP-1 agonist), which work by helping regulate appetite and supporting feelings of fullness. Clinical trials have shown average weight loss of 15–21% of body weight when used alongside a reduced-calorie diet and increased physical activity.
Eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. These are prescription-only medicines requiring a clinical assessment to determine suitability. Use our GLP-1 weight loss calculator to explore potential outcomes at different doses, and our BMI calculator to check your current classification according to NHS guidelines.
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 vs Private Access: How to Get Started
NHS access: Weight loss medications are available through specialist tier 3 or tier 4 weight management services. You'll need a referral from your GP, though regional availability varies significantly and waiting lists can be lengthy. Private access: GPhC-registered online prescribers can issue prescriptions following a clinical assessment—no NHS referral required. Both routes require a prescription and clinical review to confirm the medication is appropriate for your individual health profile.
Start by speaking to your GP about your weight management goals. They can assess whether prescription medication is suitable, refer you to NHS services if eligible, or discuss private options. Track your progress with our free progress tracker, and use our weight converter to monitor your weight in stone, lbs, or kg as you prefer.
- 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.
Can I access weight loss medication on the NHS?
Yes, GLP-1 medications are available through NHS specialist weight management services for eligible adults. You'll need a GP referral and must meet BMI or health condition criteria. Regional availability varies, so ask your GP about local services and waiting times.
What's the difference between Mounjaro and Wegovy?
Both are prescription weight loss injections used once weekly. Mounjaro (tirzepatide) uses a dual mechanism activating two hormone pathways, whilst Wegovy (semaglutide) is a single GLP-1 agonist. Clinical trials showed comparable average weight loss—around 15–21%—though individual results vary.
How quickly will I lose weight on prescription medication?
Safe and sustainable weight loss is typically 0.5–1 kg per week. Clinical trials showed average losses of 15–21% over 68–72 weeks. Results vary significantly between individuals depending on diet, activity, dose, and other factors. Your prescriber will discuss realistic expectations.
Do I need to change my diet and exercise if taking weight loss medication?
Yes. Prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. They're a tool to support behaviour change, not a replacement for it. Your GP or prescriber can recommend appropriate dietary and exercise approaches.
Is weight loss medication safe long-term?
Yes, when prescribed and monitored appropriately. Like all medicines, they have potential side effects—most commonly nausea and gastrointestinal effects that often improve over time. Your prescriber will assess suitability based on your medical history and monitor you throughout treatment.
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.