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
Cancer and Weight Loss: UK Prescription Options
Weight changes after cancer diagnosis or treatment are common and can significantly impact wellbeing and recovery. If you're seeking to manage your weight and are eligible, prescription weight management options are now available through the NHS and privately in the UK. This guide explains how medication can support weight loss goals alongside lifestyle changes, and how to find out whether treatment is right for you. Use our free BMI calculator above to understand your current health status.
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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
Three prescription-only medications are licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These GLP-1 and GIP/GLP-1 receptor agonist medications work by helping regulate appetite and supporting feeling fuller after meals, making them useful tools for structured weight management uk programmes.
- Mounjaro: Once-weekly injection, doses 2.5 mg to 15 mg. Clinical trials showed average weight loss of 15–21% body weight at maximum dose.
- Wegovy: Once-weekly injection, doses 0.25 mg to 2.4 mg. Clinical evidence demonstrates average weight loss of approximately 15% body weight.
- Saxenda: Once-daily injection, doses 0.6 mg to 3 mg. Established weight loss medication with proven efficacy in clinical trials.
All are prescription-only and require clinical assessment. Individual results vary significantly. These medications work alongside a reduced-calorie diet and increased physical activity—not as replacements for lifestyle changes.
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 in the UK
NHS access: Available through tier 3 specialist weight management services following GP referral. You'll need a BMI of 30 or above (or 27+ with weight-related health conditions) and may be assessed for eligibility including any cancer-related factors. Waiting lists vary significantly by region and availability can be limited.
Private access: Available through GPhC-registered online prescribing services following an online clinical assessment. No NHS referral needed. Your GP can provide information about whether weight loss medication nhs eligibility might apply to you personally, or you can explore private options independently. Either way, starting a conversation with your GP about prescription weight loss uk options is a positive step. Try our GLP-1 weight loss calculator to estimate potential outcomes.
- 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 use weight loss injections if I've had cancer?
Many cancer survivors are eligible for prescription weight loss medication. However, eligibility depends on individual health factors, current treatment status, and any ongoing medical conditions. Your GP or prescriber will assess your personal situation and medical history to determine suitability. Always inform your healthcare provider of your cancer history before starting any weight management treatment.
How quickly can I expect weight loss with these medications?
Weight loss typically becomes noticeable after 4–8 weeks, with most significant loss occurring in months 3–6. Clinical trials show average weight loss of 15–21% body weight over 12–18 months on maximum doses, though individual results vary. Weight loss is gradual and sustainable when combined with lifestyle changes—rapid loss is not the goal.
Do weight loss injections work alongside cancer treatment?
If you're currently undergoing cancer treatment, discuss weight management medication with your oncology team and GP first. Some medications may interact with cancer treatments or affect appetite in ways relevant to your recovery. Your healthcare team can advise on safe timing and suitability based on your specific treatment plan.
How do I know if I'm eligible for weight loss medication on the NHS?
You typically need a BMI of 30 or above, or 27+ with weight-related health conditions such as diabetes or cardiovascular disease. Start by speaking with your GP, who can refer you to your local tier 3 weight management service. They'll conduct a full assessment and discuss whether prescription weight loss treatment is appropriate for your circumstances.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates one (GLP-1 only). Mounjaro showed slightly higher average weight loss in clinical trials (~20.9% vs ~15%), but individual responses vary greatly. Your prescriber will recommend the most suitable option based on your health profile. Use our weight converter to track progress in stone and pounds.
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.