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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Mounjaro for PCOS — How It Works and Results
Mounjaro (tirzepatide) is increasingly prescribed in the UK for weight management in adults with PCOS (polycystic ovary syndrome), often alongside lifestyle changes. Both Mounjaro and Wegovy are prescription-only GLP-1 based medications available through NHS specialist services or private prescribing. This guide explains how both medications work, what clinical trial data shows, and how your GP or prescriber decides which might be suitable for you. Results vary significantly between individuals — weight loss depends on dose, adherence, diet, and physical activity.
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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.
Mounjaro vs Wegovy — Mechanism and Clinical Trial Data
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — meaning it activates two natural hormone pathways rather than one. In the SURMOUNT-1 clinical trial, participants on the maximum 15 mg dose lost an average of 20.9% of their body weight over 72 weeks. Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single pathway. In the STEP-1 trial, participants on 2.4 mg lost an average of 14.9% of body weight over 68 weeks.
- Mounjaro: Dual mechanism, starting dose 2.5 mg, maximum 15 mg weekly
- Wegovy: Single GLP-1 mechanism, starting dose 0.25 mg, maximum 2.4 mg weekly
- PCOS context: Both medications may help reduce weight and improve insulin resistance — a key factor in PCOS
The dual mechanism of Mounjaro means it may provide additional effects on appetite and glucose regulation compared to single-mechanism GLP-1 agents. However, clinical trial results are averages — individual outcomes vary considerably based on starting weight, genetics, medication adherence, and lifestyle factors.
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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.
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Eligibility, Suitability, and How Your Prescriber Decides
Both Mounjaro and Wegovy are prescription-only medicines requiring clinical assessment. Your GP or prescriber will evaluate your BMI, medical history, and PCOS management goals to determine which medication (if any) is appropriate. Use our free BMI calculator above to understand your current BMI category — this is often the starting point for eligibility conversations.
For adults with PCOS, insulin resistance and metabolic factors may influence which medication your prescriber recommends. Neither medication is a replacement for PCOS management — they work alongside metformin, lifestyle changes, and hormonal treatments. Your prescriber will consider your complete health picture, not just weight loss potential. Both require a reduced-calorie diet and increased physical activity to achieve meaningful results.
- 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 Mounjaro or Wegovy better for PCOS weight loss?
Both medications can support weight loss in PCOS, but neither is universally "better". Mounjaro's dual mechanism may benefit some people, but clinical trial averages show modest differences. Your prescriber will assess your individual health factors — insulin resistance levels, other medications, previous weight loss attempts — to recommend the most suitable option. Results vary significantly between individuals.
Can I access Mounjaro for PCOS on the NHS?
Mounjaro is available through NHS specialist tier 3 weight management services for eligible adults. You'll typically need a GP referral. Eligibility requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions (PCOS with insulin resistance may qualify). NHS availability varies by region — waiting lists can be lengthy in many areas.
What weight loss can I realistically expect with Mounjaro and PCOS?
Clinical trials showed an average of clinically studied weight loss on maximum-dose Mounjaro over 72 weeks. However, this is an average across many people — your individual result depends on starting weight, genetics, dose reached, diet adherence, and activity level. PCOS may influence weight loss differently than in people without PCOS. Your GP can discuss realistic expectations for your situation.
How long do I need to take Mounjaro or Wegovy?
Both medications are ongoing treatments, not short-term courses. You continue taking them as long as they're helping and your prescriber recommends them. If you stop, weight regain is common — weight loss is maintained through continued use alongside lifestyle changes. Your prescriber will review this regularly with you.
What's the difference between tirzepatide and semaglutide for PCOS?
Tirzepatide (Mounjaro) is a dual GIP+GLP-1 agonist; semaglutide (Wegovy) is a GLP-1-only agonist. Tirzepatide's dual action may offer additional benefits for insulin sensitivity in PCOS, but both work similarly — they reduce appetite, slow digestion, and may improve blood sugar control. Your prescriber will recommend based on your medical history and response to assessment.
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