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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Sudden Weight Loss for Women — UK Prescription Medication Guide
Sudden weight loss in women can be managed with prescription weight management medication in the UK. If you're experiencing unexplained weight loss or looking to lose weight safely, several NHS-approved options are available. This guide explains UK-licensed medications, eligibility criteria, and how to access weight management through the NHS or private prescribing. Our BMI calculator can help you understand your current weight status, and our GLP-1 weight loss calculator shows how prescription medication might support your goals alongside lifestyle 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-Licensed Weight Loss Medications for Women
Three prescription-only weight management medications are licensed in the UK for eligible women:
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist injected once weekly. Clinical trials showed an average weight loss of 15–21% of body weight over 72 weeks, though individual results vary.
- Wegovy (semaglutide) — A GLP-1 receptor agonist injected once weekly. Average weight loss in trials was approximately 14.9% of body weight, alongside a reduced-calorie diet and increased physical activity.
- Saxenda (liraglutide) — A daily GLP-1 injection, older option with average weight loss around 5–10% of body weight.
All three require a prescription following a clinical assessment. Eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease.
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. Services vary significantly by region, and waiting lists can be lengthy. NICE has approved tirzepatide (Mounjaro) for NHS use, though semaglutide (Wegovy) availability depends on your local integrated care board (ICB).
Private access: Available through GPhC-registered online prescribing services following an online clinical assessment with a UK-licensed prescriber. No NHS referral required. Costs typically range from £129–£320 per month depending on dose and provider.
Your GP can help assess whether you're eligible and discuss the best option for your circumstances. Use our free BMI calculator to check your current status before speaking with your healthcare provider.
- 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 causes sudden weight loss in women and when should I see my GP?
Sudden unintentional weight loss can indicate hormonal changes, metabolic conditions, or medical issues. If you're losing weight without trying, always see your GP first for assessment. If you're intentionally seeking weight loss, prescription medication may help if you meet NHS eligibility criteria — your GP can advise.
Am I eligible for prescription weight loss medication in the UK?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with a weight-related health condition like diabetes or high blood pressure. For South Asian, Chinese, Black African, or Black Caribbean women, lower thresholds may apply. Your GP or a prescriber can assess your individual eligibility.
How much weight can I lose with Mounjaro or Wegovy?
Clinical trials showed average weight loss of 15–21% with Mounjaro and approximately 15% with Wegovy. Individual results vary significantly and depend on dose, adherence, diet, and exercise. Results are typically achieved over several months alongside lifestyle changes.
Can I get weight loss injections on the NHS?
Yes, through specialist tier 3 weight management services. You'll need a GP referral. Availability and waiting times vary by region. Private options are also available through licensed prescribers without NHS referral, though these come at personal cost.
What are the main side effects of weight loss medication for women?
Common side effects include nausea, diarrhoea, constipation, and stomach pain — usually mild and improving over time. Oral contraceptive users need barrier protection for 4 weeks after starting and after each dose increase. Your prescriber will discuss all risks during assessment. ```
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.