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
Breast Changes After Weight Loss — What You Need to Know
Weight loss, whether through diet, exercise, or prescription medication, can affect breast tissue and composition as your body loses fat. This is a natural part of the weight loss process, though the extent varies significantly between individuals based on genetics, age, and starting weight. If you're considering weight management through UK-licensed prescription medications like Mounjaro or Wegovy, understanding these physical changes can help you make informed decisions about your health journey. Many people find that speaking with their GP about comprehensive weight management options helps address both health outcomes and personal concerns about body composition changes.
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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 Prescription Weight Loss Options and Eligibility
Several prescription-only weight loss medications are licensed in the UK and available through NHS specialist services or private prescribing. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist taken once weekly, with clinical trials showing average weight loss of 15–21% of body weight. Wegovy (semaglutide) is a GLP-1 receptor agonist also taken once weekly, with trials demonstrating around 15% average weight loss. Saxenda (liraglutide) is a daily GLP-1 injection option.
You may be eligible for prescription weight loss medication if you have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply. All prescription weight loss medications work alongside reduced-calorie diet and increased physical activity — not instead of them.
Use our GLP-1 weight loss calculator to explore projected weight loss at different medication doses, and our BMI calculator to check whether you fall within typical eligibility ranges for prescription treatment.
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 Find Out If You're Eligible
NHS access: Weight loss medications are prescribed through tier 3 specialist weight management services. You'll need a referral from your GP, and availability varies significantly by region. Waiting lists can be lengthy in many areas, but if approved, prescriptions are provided through the NHS.
Private access: UK-licensed prescribers offer online consultations and prescriptions for weight loss medication without requiring NHS referral. Following a clinical assessment, prescriptions are dispensed by GPhC-registered pharmacies. This route is typically faster but involves private costs.
Next step: Start a conversation with your GP about weight management options. Your GP can discuss which route (NHS or private) suits you best, assess your medical history, and help you understand realistic outcomes. Be open about your concerns regarding body composition changes — your healthcare team can provide personalised guidance throughout your weight loss journey.
- 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.
Does weight loss always affect breast size?
Weight loss does affect breast tissue in most people because breasts contain adipose (fat) tissue. The extent varies significantly based on genetics, age, skin elasticity, and how much weight is lost. Some people notice minimal change, whilst others experience more noticeable reduction. This is a normal physiological response to fat loss, not a medical concern.
Can prescription weight loss medications like Mounjaro or Wegovy prevent breast changes?
Prescription weight loss medications cannot selectively preserve breast tissue — they work by reducing overall body fat. However, gradual, sustained weight loss (around 0.5–1 kg per week) may minimise the appearance of changes compared to gradual weight management. The medications themselves do not directly cause breast changes; body fat reduction does.
What should I discuss with my GP about weight loss and body composition?
Tell your GP about your goals, concerns regarding body changes, and your overall health priorities. Your GP can explain realistic outcomes of weight loss, discuss whether prescription medication suits you, and signpost you to support services like nutrition advice or counselling if you're concerned about body image during your weight loss journey.
How do I know if I'm eligible for UK prescription weight loss medication?
You may be eligible if your BMI is 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure. Your GP or a licensed prescriber will assess your individual health during a consultation. Use our BMI calculator to check your current BMI and understand whether you fall within typical eligibility ranges.
What is the difference between Mounjaro and Wegovy for weight loss?
Both are once-weekly injections licensed for weight management in the UK. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist with average weight loss of 15–21%. Wegovy (semaglutide) is a GLP-1 agonist with average weight loss around 15%. Individual results vary. A prescriber will assess which is more suitable for your health profile and circumstances.
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.