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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Speedy Weight Loss Tips: UK Prescription Medication Options
Looking for effective weight loss solutions in the UK? While sustainable weight management typically involves lifestyle changes, prescription medications can support faster results for eligible adults. This guide covers UK-licensed weight loss injections, how they work, who qualifies, and how to access them through the NHS or private prescribing. Our GLP-1 weight loss calculator can help you estimate potential results with prescription weight management options.
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 Medications Available Now
The UK has three prescription-only weight loss medications licensed for adults:
- Mounjaro (tirzepatide) — dual GIP and GLP-1 receptor agonist. Once-weekly injection. Doses range from 2.5 mg to 15 mg. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks when combined with diet and exercise.
- Wegovy (semaglutide) — GLP-1 receptor agonist. Once-weekly injection. Maximum dose 2.4 mg. Average weight loss approximately 15% of body weight in clinical trials.
- Saxenda (liraglutide) — GLP-1 receptor agonist. Daily injection. Maximum dose 3 mg. Approved for weight management in UK adults.
All require a prescription following clinical assessment. Eligibility includes adults with a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds may apply.
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 Medication: NHS vs Private Routes
NHS route: Request a referral from your GP to a tier 3 specialist weight management service. NHS availability varies significantly by region, and waiting lists can be lengthy in many areas. Once referred, a specialist team will assess your eligibility and manage your treatment.
Private route: Online consultation with a UK-licensed prescriber through a registered pharmacy. No NHS referral needed. Available if you meet eligibility criteria. Costs typically range from £129–£320 monthly depending on dose.
Whichever route you choose, remember that prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. Track your progress with our free progress tracker to monitor results alongside lifestyle changes.
- 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 get weight loss medication on the NHS quickly?
NHS waiting times vary by region. Many areas have significant waiting lists for specialist weight management services. Private prescription options are available if you meet eligibility criteria and prefer faster access. Contact your local NHS weight management service to find out typical waiting times in your area.
What's the difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP and GLP-1 agonist, while Wegovy is a GLP-1 agonist only. Clinical trials showed Mounjaro may produce slightly higher average weight loss (15–21% vs approximately 15% for Wegovy), though individual results vary significantly. Both are once-weekly injections and require prescription.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions (diabetes, high blood pressure, sleep apnoea, cardiovascular disease). South Asian, Chinese, Black African, or Black Caribbean adults may qualify at lower BMI thresholds. A prescriber will assess your individual eligibility.
How long does it take to see weight loss results?
Initial changes may be noticed within 2–4 weeks. Significant weight loss typically becomes apparent after 8–12 weeks. The NHS recommends expecting 0.5–1 kg per week loss, though results vary based on dose, diet, and exercise. Use our BMI calculator to track your progress and check your BMI category over time.
Are weight loss injections safe long-term?
Prescription weight loss medications have been studied in clinical trials lasting up to 68 weeks. Side effects are generally manageable and reduce over time as your body adjusts. Your prescriber will monitor your progress and check for any concerning effects. Discuss long-term safety concerns with your GP or prescriber.
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.