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 vs Wegovy for PCOS: What's the Difference?
PCOS (polycystic ovary syndrome) is a hormonal condition that often makes weight management challenging. Both Mounjaro and Wegovy are prescription-only GLP-1-based injections licensed in the UK for weight management in adults with weight-related health conditions. If you have PCOS and excess weight, understanding how these medications differ can help you discuss options with your GP or prescriber. This guide compares the two based on clinical trial data, mechanism of action, and UK eligibility.
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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
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. It activates two separate hormone pathways — both GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 — which may enhance appetite suppression and metabolic effects compared to single-pathway medications.
Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single hormone pathway. Both approaches work by signalling fullness to the brain, slowing stomach emptying, and supporting reduced food intake alongside a reduced-calorie diet and physical activity.
Clinical trial context: In the SURMOUNT-1 trial, Mounjaro at 15 mg showed average weight loss of approximately 20.9% of body weight over 72 weeks. In the STEP-1 trial, Wegovy at 2.4 mg showed average weight loss of approximately 14.9% over 68 weeks. However, individual results vary significantly, and trial participants also followed dietary and exercise guidance.
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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 Medication Might Suit PCOS? Prescriber Assessment
Both Mounjaro and Wegovy require a UK prescription and clinical assessment before use. Your GP or a licensed prescriber will evaluate your individual health profile, including PCOS status, other health conditions, current medications, and personal preferences, to determine which (if either) is most suitable.
PCOS often involves insulin resistance, which some evidence suggests may respond well to dual-pathway medications like Mounjaro, though this is not a assures. Your prescriber may also consider factors like injection frequency preference (both are once-weekly), side effect profile tolerance, and cost. Use our free GLP-1 weight loss calculator to explore projected outcomes at different doses, and our BMI calculator to understand your current health metric context before your appointment.
- 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.
Can I use Mounjaro or Wegovy if I have PCOS?
Both Mounjaro and Wegovy are prescription-only. You may be eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions (which can include PCOS complications like prediabetes). Your GP or prescriber will assess your individual suitability based on your medical history, current medications, and PCOS severity.
Is Mounjaro better than Wegovy for PCOS weight loss?
Clinical trials showed different average weight loss results, but "better" depends on individual factors. Mounjaro's dual mechanism may appeal to those with insulin resistance, but Wegovy's established track record and slightly lower starting dose suit others. Only a prescriber can recommend which is appropriate for your specific situation.
What's the difference in how Mounjaro and Wegovy are dosed?
Mounjaro starts at 2.5 mg and increases to a maximum of 15 mg, with 4 weeks between dose increases. Wegovy starts at 0.25 mg and increases to 2.4 mg maximum over 16 weeks. Both are injected once weekly. Your prescriber will guide titration based on your response and tolerance.
Do I need an NHS referral to access Mounjaro or Wegovy for PCOS?
NHS access requires referral to a specialist tier 3 weight management service, which can involve long waiting lists. Private access is available through online prescribers following a clinical assessment. Costs vary by dose and provider. Always use a GPhC-registered pharmacy regardless of route.
Can Mounjaro or Wegovy help PCOS symptoms beyond weight loss?
These medications are licensed specifically for weight management. Some evidence suggests weight loss itself can improve PCOS symptoms (irregular periods, fertility, insulin resistance), but the medications don't treat PCOS directly. Your GP should manage PCOS holistically alongside any weight loss treatment.
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