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
Weight Loss Presents — What Works in the UK?
Weight loss presents many different options for UK adults, from straightforward lifestyle changes to prescription medication support. Whether you're looking to lose weight through diet and exercise, or exploring prescription options like GLP-1 weight loss injections, it's important to understand what evidence supports each approach. This guide covers the most effective and accessible weight management options available in the UK today, along with how to access them through the NHS or privately.
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.
Weight Loss Options Available in the UK
Weight management in the UK operates across four tiers of support. Tier 1 includes self-help approaches using free tools and digital programmes. Try our free BMI calculator and weight converter above to understand your current position, then use our GLP-1 weight loss calculator to explore potential results if medication becomes relevant. Tier 2 involves primary care support from your GP, often including behaviour change programmes like the NHS Weight Loss Plan. Tier 3 brings specialist multidisciplinary teams offering structured interventions and prescription weight management options. Tier 4 includes bariatric surgery for severe obesity with significant health complications.
- Self-management: Calorie deficit of around 500 kcal per day typically supports loss of approximately 0.5 kg per week
- Prescription weight loss medication: GLP-1 injections (Wegovy, Mounjaro) may help when other methods alone aren't sufficient
- NHS access: Available through tier 3 specialist services; eligibility varies by region and waiting lists can be lengthy
- Private access: Available through GPhC-registered online pharmacies following clinical assessment
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.
Understanding Your Weight Loss Eligibility
In the UK, prescription weight loss medication eligibility is based on BMI and health status. Adults with a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions (such as type 2 diabetes, high blood pressure, or sleep apnoea), may be eligible. Lower thresholds apply for adults of South Asian, Chinese, Black African, or Black Caribbean heritage due to higher health risks at lower BMI levels. Use our free BMI calculator on this page to check your current BMI. Prescription options require assessment by a licensed prescriber — your GP can refer you to NHS specialist services, or you can access private prescribing through a clinical consultation. Individual results vary significantly, and medications work best alongside reduced-calorie diet and increased physical activity.
- 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 Wegovy and Mounjaro for weight loss?
Both are prescription-only GLP-1 receptor agonist injections available in the UK. Wegovy (semaglutide) is a GLP-1 agonist; Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist. In clinical trials, Mounjaro showed slightly higher average weight loss (around 20.9% at maximum dose) compared to Wegovy (around 14.9%), though individual results vary significantly. Both require a prescription and clinical assessment.
Can I get weight loss injections on the NHS?
Yes, GLP-1 medications are available through NHS tier 3 specialist weight management services. However, NHS availability varies significantly by region and waiting lists can be very long — sometimes several months to over a year depending on your area. Your GP can refer you to your local specialist service. Private access through online prescribing is available without NHS referral.
How quickly will I lose weight on prescription medication?
Clinical trials showed average weight loss of 15–21% of body weight over 68–72 weeks with GLP-1 medications, though individual results vary considerably. The NHS recommends losing no more than 0.5–1 kg per week for sustainable results. Weight loss depends on the dose, your starting weight, adherence to treatment, and lifestyle changes including diet and physical activity.
What if I don't want prescription medication — what are my options?
Evidence-based non-medication options include calorie deficit dieting (500 kcal/day deficit typically supports 0.5 kg/week loss), increased physical activity, and behaviour change support. The NHS Weight Loss Plan offers free digital support through tier 1 and 2 services. Mediterranean and lower-carbohydrate diets have good evidence for sustainable weight loss. Speak to your GP about what suits your circumstances best.
How do I know if I'm eligible for weight loss treatment in the UK?
Use our free BMI calculator on this page to check your starting point. You're generally eligible for prescription options if your BMI is 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes or high blood pressure. Lower BMI thresholds apply for certain ethnic groups. Your GP or a licensed prescriber can assess your individual eligibility following a clinical consultation.
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.