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- 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 Weight Loss: Mounjaro vs Wegovy
Polycystic ovary syndrome (PCOS) affects weight management due to insulin resistance and hormonal factors. Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription weight loss injections licensed in the UK that may help support weight loss alongside lifestyle changes in people with PCOS. This guide compares the two weekly weight loss injection options to help you understand the differences. The choice between them is individualised — your prescriber will assess which may be more suitable based on your health profile and clinical need.
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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.
How Mounjaro and Wegovy Work Differently for PCOS
Mounjaro is a dual GIP and GLP-1 receptor agonist — it activates two natural hormone pathways simultaneously. GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) both regulate appetite and blood sugar control. This dual mechanism may be particularly relevant for PCOS, where insulin resistance is a core feature. In the SURMOUNT-1 clinical trial, Mounjaro 15 mg achieved average weight loss of approximately 20.9% over 72 weeks alongside a reduced-calorie diet and physical activity.
- Wegovy is a GLP-1 receptor agonist only — it activates one hormone pathway. The STEP-1 trial showed average weight loss of approximately 14.9% at 68 weeks on 2.4 mg with lifestyle changes.
- Both are once-weekly injections available as pre-filled pens (Mounjaro KwikPen, Wegovy pen).
- Both require a UK prescription following a clinical assessment by a licensed prescriber.
Clinical trial data suggests Mounjaro may produce greater average weight loss, though individual results vary considerably. For PCOS specifically, the dual mechanism of Mounjaro may offer additional metabolic benefit, but both medications can support insulin sensitivity improvements.
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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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Which Is Right for You? Individual Assessment Matters
Neither Mounjaro nor Wegovy is automatically "better" — suitability depends entirely on your individual health profile, medical history, and prescriber assessment. Your GP or weight management specialist will consider: your current BMI and weight-related health conditions, any other medications you take, your metabolic profile, and how you respond to clinical trials data. Both medications are prescription-only and require a formal clinical assessment before being prescribed. Access in the UK is through NHS specialist tier 3/4 weight management services or private prescribing following an online clinical consultation. Try our free GLP-1 weight loss calculator to explore projected outcomes at different doses, and use our BMI calculator to understand your starting point for any weight management discussion with your prescriber.
- 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 better than Wegovy for PCOS specifically?
Clinical trial data suggests Mounjaro's dual GIP+GLP-1 mechanism may offer additional benefit for insulin resistance, a core PCOS feature. However, individual responses vary. Both medications may help support weight loss and insulin sensitivity in PCOS. Your prescriber will assess which suits your specific health profile best.
What's the difference between a GLP-1 and a GIP+GLP-1 medication?
GLP-1 (Wegovy) activates one hormone pathway controlling appetite and blood sugar. GIP+GLP-1 (Mounjaro) activates two pathways simultaneously. The dual mechanism may provide additional metabolic regulation, particularly relevant for PCOS where insulin resistance is significant.
How much weight loss can I expect with Mounjaro or Wegovy for PCOS?
Clinical trials show average weight loss of approximately 15–21% body weight with Mounjaro and 15% with Wegovy alongside diet and activity changes. PCOS-specific outcomes may vary. Individual results depend on starting weight, adherence, lifestyle factors, and metabolic response. Your prescriber can discuss realistic expectations.
Can I get Mounjaro or Wegovy through the NHS for PCOS weight management?
Yes, both are available through NHS specialist tier 3/4 weight management services if you meet eligibility criteria (BMI ≥30, or ≥27 with weight-related health conditions like PCOS). Availability and waiting times vary by region. Private prescribing is also available through UK-licensed online prescribers.
Do I need a clinical assessment before starting either medication?
Yes, both Mounjaro and Wegovy require a prescription and clinical assessment by a UK-licensed healthcare professional. Your medical history, current medications, and health conditions must be reviewed to ensure suitability. This applies to both NHS and private routes.
Ready to take control of your weight loss journey?
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