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
Causes of Weight Loss in Females
Weight loss in females can happen intentionally through diet and exercise, or unintentionally due to underlying health conditions, stress, or medication side effects. If you're experiencing unexplained weight loss, it's important to speak to your GP to rule out medical causes. For those seeking intentional weight management in the UK, prescription options are now available through NHS specialist services or private prescribing following a clinical assessment.
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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 Management Options for Females
Three prescription-only weight management medications are currently licensed in the UK for women with a BMI of 30 or above, or 27 or above with weight-related health conditions:
- Mounjaro (tirzepatide) — a once-weekly injection that activates dual GIP and GLP-1 pathways. Clinical trials showed average weight loss of around 15–21% of body weight at the highest dose.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection with average weight loss of approximately 15% in clinical trials.
- Saxenda (liraglutide) — a once-daily GLP-1 injection, though less commonly prescribed in the UK than the weekly options.
All three work alongside reduced-calorie diet and increased physical activity. Individual results vary significantly. Use our free GLP-1 weight loss calculator to explore projected outcomes at different doses, and our BMI calculator to check your current weight management category.
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: How to Access Weight Loss Medication
NHS access: Prescription weight loss medication is available through specialist tier 3 and tier 4 weight management services. Ask your GP for a referral. Waiting lists vary significantly by region (ICB area). Private access: Available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber — no NHS referral needed. Costs typically range from £130–£320 per month depending on dose.
Before starting any prescription weight management medication, a prescriber will assess your medical history, current medications, and individual circumstances. Your GP can also advise whether medication is appropriate for you alongside lifestyle changes. Track your progress with our free progress tracker once you've started 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.
What causes unintentional weight loss in women?
Unintentional weight loss can result from thyroid disorders, diabetes, depression, anxiety, certain medications, malabsorption conditions, or serious illnesses. Stress and inadequate calorie intake also contribute. Always consult your GP if you're losing weight without trying, as it may indicate an underlying health condition requiring investigation.
Are weight loss injections available on the NHS for women?
Yes. Mounjaro and Wegovy are available through NHS specialist weight management services for eligible women (BMI 30+, or 27+ with weight-related conditions). Access is through referral to tier 3 services. Availability varies by region, and waiting lists can be lengthy. Ask your GP about eligibility in your area.
What is the difference between Mounjaro and Wegovy for females?
Mounjaro is a dual GIP/GLP-1 agonist with slightly higher average weight loss (15–21%) versus Wegovy's GLP-1-only mechanism (around 15%). Both are once-weekly injections. Clinical trials show varying outcomes between individuals. Your prescriber will recommend the most suitable option based on your health profile.
How quickly will I see weight loss results with prescription medication?
Weight loss typically becomes noticeable after 4–8 weeks, with most significant results over 12–24 weeks as doses are gradually increased. The NHS recommends losing no more than 0.5–1 kg per week for sustainable results. Individual outcomes vary considerably based on adherence, diet, activity, and metabolism.
Do I need to change my diet if I take weight loss medication?
Yes. Prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. Medication supports appetite regulation and fullness, but dietary and lifestyle changes remain essential for sustainable weight loss. Your GP or specialist can refer you to a dietitian for personalised guidance.
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.