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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Weight Loss Medication Available in the UK
If you're searching for weight loss clinic options, prescription weight management medication is available in the UK through both NHS specialist services and private prescribing routes. Unlike general weight loss clinics, medications like Mounjaro and Wegovy offer evidence-based, prescription-only support for eligible adults. This guide explains your options, eligibility criteria, and how to access weight loss medication through the UK health system—whether you prefer NHS routes or private prescribing pathways.
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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 and Eligibility
Three prescription-only medications are currently licensed in the UK for weight management: Mounjaro (tirzepatide), a dual GIP and GLP-1 injection; Wegovy (semaglutide), a GLP-1 injection; and Saxenda (liraglutide), a daily GLP-1 injection. All require a prescription and clinical assessment before dispensing.
You may be eligible if you have:
- A BMI of 30 kg/m² or above, OR
- A BMI of 27–29.9 kg/m² with at least one weight-related health condition (type 2 diabetes, high blood pressure, cardiovascular disease, or sleep apnoea)
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply—eligibility may begin at BMI 27.5 or above due to higher health risks at lower weights. In clinical trials, Mounjaro helped participants lose an average of 15–21% of body weight, whilst Wegovy achieved approximately 15% average weight loss—though individual results vary significantly and require lifestyle changes alongside medication.
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: Finding Your Route to Treatment
The NHS route involves referral to a specialist tier 3 or 4 weight management service through your GP. However, NHS availability varies significantly by region and waiting lists can extend several months. Many areas have limited capacity for specialist referrals. The private route offers faster access through online consultations with UK-licensed prescribers; if clinically appropriate following assessment, a prescription is issued and dispensed by a GPhC-registered pharmacy. To explore your options, start by speaking with your GP about NHS referral eligibility or asking for advice on private prescribing services. Our free BMI calculator and GLP-1 weight loss calculator can help you understand your current BMI and estimate potential outcomes at different medication doses—useful information to bring to your consultation.
- 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's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist with a maximum dose of 15 mg weekly, whilst Wegovy (semaglutide) is a GLP-1 agonist with a maximum dose of 2.4 mg weekly. Clinical trials showed Mounjaro achieved slightly higher average weight loss (15–21%) compared to Wegovy (approximately 15%), though individual results vary. Both are once-weekly injections requiring prescription and clinical assessment.
How do I know if I'm eligible for prescription weight loss medication?
You're typically eligible if your BMI is 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or cardiovascular disease. For South Asian, Chinese, Black African, or Caribbean adults, lower thresholds apply. Your GP can assess your individual eligibility and discuss options with you—this is the best starting point.
Can I get weight loss medication through the NHS in the UK?
Yes, but access varies by region. You'll need a GP referral to a specialist NHS weight management service (tier 3 or 4). These services assess eligibility and may prescribe medications like Mounjaro or Wegovy. However, waiting lists can be very long in many areas, sometimes several months. Private prescribing offers faster access if you meet clinical criteria.
What are the main side effects of weight loss injections?
Common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain—especially during dose escalation. Most people adjust within a few weeks. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) or gallbladder problems. Always discuss side effects with your prescriber and report anything concerning immediately.
How much weight can I realistically expect to lose?
Clinical trials show average weight loss of 15–21% of body weight with Mounjaro and approximately 15% with Wegovy over 68–72 weeks, alongside reduced-calorie diet and increased physical activity. However, individual results vary significantly—some people lose more, some less. Weight loss depends on adherence, lifestyle changes, genetics, and other factors. Your prescriber can discuss realistic expectations for your situation.
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.