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
Weight Loss Injections in the UK: What You Need to Know
Weight loss injections are prescription medications licensed in the UK for adults with overweight or obesity. If you've seen discussions on Mumsnet or other forums about GLP-1 weight loss medications, this guide explains what's actually available through the NHS and private prescribers, how eligibility works, and what the evidence shows. Whether you're exploring prescription weight management UK options or simply want to understand what these medications are, we'll cover the key facts in straightforward terms.
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 Weight Loss Injection Options
Three prescription weight loss injections are currently licensed for use in the UK: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro and Wegovy are once-weekly injections; Saxenda is a daily injection. All three work as GLP-1 receptor agonists (or in Mounjaro's case, a dual GIP/GLP-1 agonist), which means they activate natural hormone pathways that help regulate appetite and support feeling fuller after meals.
Clinical trials show these medications can help adults lose weight alongside a reduced-calorie diet and increased physical activity. On average, Mounjaro users lost 15–21% of their body weight in trials, whilst Wegovy users lost approximately 15%. Results vary significantly between individuals. To check if your personal weight falls into a range where medication might be considered, use our free BMI calculator above—this gives you an instant picture of your starting point before speaking to a healthcare professional.
- All three are prescription-only — they cannot be bought over the counter
- Each requires a clinical assessment before being prescribed
- Individual eligibility depends on BMI, health conditions, and other factors
- Not suitable during pregnancy or breastfeeding
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 Prescribing in the UK
NHS route: Weight loss medications are available through NHS tier 3 specialist weight management services. You'll need a referral from your GP. However, availability varies significantly by region, and waiting lists can be lengthy in many areas. NICE has approved tirzepatide (Mounjaro) within specialist NHS services, but access depends on your local integrated care board (ICB) and current commissioning.
Private route: You can obtain a prescription through a GPhC-registered online prescriber following a clinical assessment, without an NHS referral. Costs vary by medication and dose (typically £120–£320 per month depending on the injection and starting dose). If you're interested in exploring options, our free GLP-1 weight loss calculator can help you understand projected results at different doses. Your GP can discuss which route—NHS or private—might be most appropriate for your situation.
- Always speak to your GP first, even if considering private options
- A prescriber will assess your medical history and suitability
- Weight loss medication works best alongside lifestyle changes, not instead of them
- 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 injections available on the NHS in the UK?
Yes, Mounjaro (tirzepatide) and other GLP-1 medications are available through NHS specialist weight management services following a GP referral. However, availability varies by region and waiting lists can be very long. Your GP can advise whether you'd be eligible and how to access NHS services in your area.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections for weight management, but they work slightly differently. Mounjaro is a dual GIP/GLP-1 agonist; Wegovy is a GLP-1 agonist only. In clinical trials, Mounjaro showed slightly higher average weight loss (15–21% vs 15%), but individual results vary. A prescriber can discuss which might suit your circumstances.
Who is eligible for weight loss injections in the UK?
Adults with a BMI of 30 or above, or 27–29.9 with a weight-related health condition (such as type 2 diabetes, high blood pressure, or sleep apnoea), may be eligible. Lower BMI thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Your GP or prescriber will assess your individual situation.
Can I get weight loss injections privately if the NHS waiting list is too long?
Yes. Private GPhC-registered prescribers can issue prescriptions for weight loss medications following an online clinical assessment. You don't need an NHS referral. Costs vary by medication and dose, typically between £120–£320 per month. Always inform your GP of any medication you're taking.
What side effects should I expect from weight loss injections?
Common side effects include nausea, diarrhoea, constipation, and stomach discomfort—especially during the first few weeks. These often improve as your body adjusts. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) or allergic reactions. Always report any concerning symptoms to your prescriber immediately.
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.