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
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Weight Loss During and After Cancer — UK Health Guide
Weight changes are common during and after cancer treatment, and managing your health at this time requires specialist care. While weight loss medications are available in the UK for eligible adults, cancer patients need individualised support from their healthcare team. This guide explains prescription weight management options in the UK, NHS support available to cancer patients, and when to speak with your GP or oncology team about weight-related concerns.
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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 Weight Management Options for Cancer Patients
If you've experienced weight changes related to cancer treatment, several prescription weight management options are available in the UK, but suitability must be assessed individually by your healthcare team. GLP-1 medications including Mounjaro (tirzepatide) and Wegovy (semaglutide) are licensed for weight management in UK adults with specific BMI thresholds, though eligibility and safety depend on your personal health history and current treatment status.
- Mounjaro (tirzepatide): A dual GIP and GLP-1 receptor agonist, administered once weekly. Clinical trials showed average weight loss of 15–21% of body weight, though individual results vary significantly.
- Wegovy (semaglutide): A GLP-1 receptor agonist, also once weekly. Average weight loss in trials was approximately 15% of body weight alongside lifestyle changes.
- Saxenda (liraglutide): A daily GLP-1 injection, available in the UK for weight management in eligible adults.
All prescription weight loss medication requires a clinical assessment and must be prescribed by a GP or specialist. Cancer patients must discuss any weight management plans with their oncology team to ensure safety alongside treatment protocols.
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 Support and How to Get Help
The NHS offers weight management support through tier 1–3 services, including lifestyle programmes, digital tools, and in some cases prescription medication through specialist services. Access to prescription weight loss treatment via the NHS typically requires referral to a tier 3 specialist weight management service, availability varies by region, and waiting times can be lengthy.
Private prescribing is also available through UK-licensed online prescribers following a clinical assessment—many cancer patients find this faster. Crucially, your GP or oncology team should be informed of any weight management treatment you pursue. Use our free BMI calculator above to understand your current weight health context, and always discuss weight changes with your healthcare team before starting any new medication or programme.
- 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.
Is it safe to take weight loss medication if I've had cancer?
Weight loss medication safety for cancer patients depends on your individual health history, current treatment status, and type of cancer. You must discuss any weight management medication with your oncology team and GP before starting. They will assess whether it's safe for you based on your specific circumstances. Never start weight loss medication without professional medical advice.
Can I get weight loss injections on the NHS if I'm a cancer patient?
NHS prescription weight loss medication is available through specialist tier 3 weight management services in some regions, but access varies significantly. Cancer patients may have additional considerations affecting eligibility and safety. Contact your GP to ask about NHS weight management services in your area, or discuss with your oncology team about appropriate support options during and after treatment.
What should I do if I've lost weight due to cancer treatment?
Weight loss during cancer treatment is common and your healthcare team should monitor this. Speak with your GP, oncology team, or a registered dietitian about the best approach for your situation. They may recommend nutritional support, lifestyle adjustments, or—if appropriate and after assessment—other options. Our free BMI calculator can help you track your weight context, but professional medical guidance is essential during cancer care.
What's the difference between cancer-related weight loss and other weight loss?
Cancer-related weight loss (cachexia) involves muscle and fat loss driven by the disease and treatment, which differs from weight loss from calorie deficit alone. Cancer cachexia requires specialist nutritional and medical management. Standard weight loss approaches may not be appropriate or effective. Always work with your oncology team and a dietitian experienced in cancer care to address weight changes safely.
How do I start a conversation with my GP about weight management after cancer?
Book an appointment with your GP and explain your weight concerns following cancer treatment. Be honest about any weight changes you've experienced and your health goals. Your GP can assess your current health, refer you to appropriate support (dietitian, specialist services, or counselling), and discuss whether prescription weight management medication might be suitable. Written down your weight history and health concerns beforehand.
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.