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
How to Quicken Weight Loss: Prescription Options Available in the UK
If you're looking to speed up weight loss, prescription medications may be an option worth discussing with your GP. While healthy weight loss typically means losing 0.5–1 kg per week through diet and exercise alone, some UK adults are eligible for prescription weight management medicines that can help accelerate results. This guide explains the prescription weight loss options available in the UK, who qualifies, and how to find out if medication might support your health goals.
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 Prescription Weight Loss Medications
Three prescription medications are licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are known as GLP-1 receptor agonist medications — they work by helping regulate appetite, reduce food cravings, and support feeling fuller after meals.
Clinical evidence: In SURMOUNT-1 trials, Mounjaro helped participants lose an average of 15–21% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity. Wegovy (in STEP trials) showed average weight loss of approximately 15% body weight. Individual results vary significantly.
You typically become eligible if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI thresholds due to higher health risks at the same BMI.
- All three are prescription-only medicines requiring clinical assessment
- Available through NHS specialist weight management services or private prescribing
- Used alongside lifestyle changes — not as a standalone treatment
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.
Getting Started: NHS vs Private Routes
NHS route: Ask your GP for a referral to your local tier 3 specialist weight management service. They'll assess your eligibility and may prescribe medication if appropriate. However, NHS availability and waiting times vary significantly by region.
Private route: GPhC-registered online prescribing services can issue prescriptions following a digital clinical assessment — you don't need an NHS referral. This is often faster but involves private costs, typically £129–£320 per month depending on dose.
Calculate your BMI using our free BMI calculator on this page to understand where you stand. A GP or licensed prescriber can then discuss whether prescription weight loss medication is right for you. Many people benefit from combining medication with the guidance of a progress tracker to monitor results over time.
- 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.
How much faster can I lose weight with prescription medication?
Clinical trials show prescription weight loss medications help people lose an average of 15–21% of body weight over 12–18 months, alongside diet and exercise. This is faster than diet and exercise alone, but individual results vary. Speed depends on the dose, your metabolism, and how strictly you follow dietary changes.
Am I eligible for prescription weight loss medication on the NHS?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure. Lower BMI thresholds apply to South Asian and Black African heritage adults. Your GP can assess your individual eligibility during a consultation.
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. Wegovy (semaglutide) is a single GLP-1 agonist with a maximum dose of 2.4 mg weekly. Clinical trials suggest similar average weight loss, but individual responses differ. Your prescriber will advise which is most appropriate.
Can I get prescription weight loss medication quickly in the UK?
NHS waiting times vary by region — some areas have waits of several months. Private online prescribing is faster, typically issuing prescriptions within days of assessment. Both routes require a clinical assessment to ensure the medication is safe and suitable for you.
Do I need to diet and exercise if I take weight loss medication?
Yes. Prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. Medication helps manage appetite and supports your efforts, but lifestyle changes remain essential for sustainable weight loss and long-term health benefits.
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.