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
Quick Weight Loss Diet Plan: UK Medication Options
gradual weight management rarely works long-term, but prescription weight management medication can support sustainable results when combined with diet and lifestyle changes. In the UK, several evidence-based options are available — including GLP-1 injections like Mounjaro and Wegovy — for adults who meet specific eligibility criteria. This guide covers what's available, how to access treatment through the NHS or privately, and how medication can fit into a realistic weight loss strategy alongside dietary changes and increased physical activity.
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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 Options
Three prescription medications are currently licensed in the UK for weight management in adults:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 injection, once weekly. Clinical trials showed an average weight loss of 15–21% of body weight over 72 weeks, though individual results vary.
- Wegovy (semaglutide) — a GLP-1 injection, once weekly. Average weight loss in trials was approximately 15% of body weight, alongside a reduced-calorie diet and increased physical activity.
- Saxenda (liraglutide) — a GLP-1 injection, once daily. Available as a daily alternative to weekly options.
You are eligible if your BMI is 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, prediabetes, high blood pressure, or sleep apnoea. For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds may apply. Calculate your personal BMI using our free BMI calculator above to check where you stand.
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 route: Ask your GP for a referral to your local tier 3 specialist weight management service. These provide comprehensive support including behavioural coaching, dietary guidance, and medication prescription where appropriate. However, waiting times vary significantly across regions and can be lengthy in many areas.
Private route: Prescription weight loss medication is available through UK-licensed online prescribers and pharmacies. You'll complete an online clinical assessment; if suitable, a prescription is issued and dispensed by a GPhC-registered pharmacy. This route typically offers faster access but involves direct costs (usually £130–£320 monthly depending on dose).
Whichever route you choose, weight loss medication works best alongside sustainable dietary changes. Our GLP-1 weight loss calculator can help you understand potential outcomes at different medication doses.
- 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 quick weight loss without prescription medication?
Yes. A calorie deficit of around 500 kcal per day (through diet and exercise) typically results in approximately 0.5 kg of sustainable weight loss per week. The NHS recommends this approach first. However, if you have a BMI of 27 or above with weight-related health conditions, prescription medication may be an option to discuss with your GP.
Are GLP-1 injections safe for long-term use?
GLP-1 medications are approved for ongoing use in the UK and have been studied for safety over several years. Like all medicines, they have potential side effects — commonly nausea, diarrhoea, and constipation — which often improve over time. Your prescriber will monitor you regularly. Always discuss risks and benefits with your GP or prescriber.
How quickly will I lose weight on Mounjaro or Wegovy?
Weight loss is gradual. In clinical trials, the maximum dose took 16–20 weeks to reach. Most people notice modest weight loss within the first month, with continued loss over several months. Average weight loss was 15–21% of body weight over one year, but individual results vary significantly based on diet, exercise, and other factors.
Can I get prescription weight loss medication on the NHS?
Yes, but access is through specialist tier 3 weight management services, not standard GP prescription. You'll need a referral from your GP. Availability varies significantly by region and waiting lists can be long. Private access is faster but involves direct costs. Ask your GP about options in your area.
What if I don't qualify for prescription medication?
You can still achieve sustainable weight loss through calorie deficit (diet and exercise), dietary approaches like the Mediterranean diet or intermittent fasting, and NHS community weight management programmes. Track your progress with our free progress tracker. If your circumstances change — such as developing a weight-related health condition — you may become eligible for medication in future.
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.