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
What Helps With Weight Loss in the UK
Weight loss is a complex health issue with many contributing factors. Lifestyle changes like reduced-calorie diets and increased physical activity form the foundation, but for many UK adults, prescription weight management medication can provide significant additional support. If you're struggling to lose weight, several NHS-approved options are available — from structured weight loss programmes to prescription medications like Mounjaro and Wegovy. Understanding what helps with weight loss starts with assessing your personal situation, BMI, and eligibility for different treatments. This guide covers prescription medication options available in the UK and how to find out if you qualify.
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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 — What Works
Three prescription-only weight loss medications are currently licensed in the UK for adults with overweight or obesity:
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist given as a once-weekly injection. Clinical trials showed participants lost an average of 15–21% of their body weight alongside diet and exercise changes.
- Wegovy (semaglutide) — A GLP-1 receptor agonist given as a once-weekly injection. Trials demonstrated average weight loss of approximately 15% of body weight.
- Saxenda (liraglutide) — A GLP-1 receptor agonist given as a once-daily injection, typically used when weekly options are unsuitable.
You may be eligible if you have a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply. Use our free BMI calculator to check your current BMI and see where you fall within NHS guidelines. Individual results vary significantly — weight loss medication works best when combined with dietary changes and increased physical activity, not as a replacement for lifestyle adjustments.
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: You can be referred by your GP to a specialist tier 3 weight management service. However, NHS access varies significantly by region and waiting times can be lengthy. Your GP will assess whether prescription weight loss medication is appropriate based on your health profile.
Private route: Prescription weight loss medication is available through private online prescribing services following an online clinical assessment with a UK-licensed prescriber. This often provides faster access without NHS waiting lists.
Whichever route you choose, speak with your GP first about your weight loss goals and health concerns. They can advise on NHS availability in your area and whether prescription medication might help you. Our GLP-1 weight loss calculator can help you estimate potential results at different medication doses — useful information to discuss during your GP 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 is a GLP-1 weight loss injection and how does it work?
GLP-1 receptor agonist injections mimic a natural gut hormone that signals fullness to the brain, reduces appetite, and slows stomach emptying. Medications like Wegovy and Saxenda use this mechanism. Mounjaro is even more effective because it activates two pathways (GIP and GLP-1). All are prescription-only and work best with diet and exercise changes.
Am I eligible for prescription weight loss medication in the UK?
You may be eligible if your BMI is 30 or above, or 27–29.9 with weight-related health conditions (diabetes, high blood pressure, sleep apnoea). Lower thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Your GP or a licensed prescriber can assess your individual eligibility after a clinical assessment.
How much weight will I lose with Mounjaro or Wegovy?
Clinical trials showed average weight loss of 15–21% of body weight with Mounjaro and approximately 15% with Wegovy — but individual results vary significantly. Some people lose more, others less. Weight loss medication works alongside reduced-calorie diet and increased physical activity, not instead of them.
What are the common side effects of weight loss injections?
The most common side effects are nausea, diarrhoea, vomiting, and constipation — especially when starting or increasing doses. These often improve over time. Less common are headache, fatigue, and injection site reactions. Always discuss side effects with your prescriber before starting treatment.
Can I access weight loss medication on the NHS in my area?
NHS access to weight loss medication varies significantly by region and specialist service availability. Waiting times can be several months to over a year in many areas. Your GP can refer you to your local tier 3 weight management service, or you can explore private prescribing options for faster access.
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.