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: Before and After Expectations
PCOS (polycystic ovary syndrome) often makes weight management more difficult due to insulin resistance, but Mounjaro (tirzepatide) may help. This guide explains how Mounjaro works for PCOS, what clinical evidence shows, and what realistic expectations look like. Individual results vary significantly, and weight loss is always most effective alongside a reduced-calorie diet and increased physical activity. Use our free weight loss calculator and BMI calculator to see where you are now and track your progress.
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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.
How Mounjaro May Help PCOS Weight Management
Mounjaro is a dual GIP and GLP-1 receptor agonist — it works differently from standard weight loss approaches because it targets two hormone pathways involved in appetite regulation and insulin function. For people with PCOS, this is potentially important: PCOS is strongly linked to insulin resistance, which makes it harder for the body to regulate blood sugar and can drive weight gain. By supporting better insulin sensitivity and reducing appetite, Mounjaro may help address both the metabolic and appetite-related drivers of weight gain in PCOS.
What clinical evidence shows: Clinical trials (SURMOUNT-1 and SURMOUNT-4) demonstrated that on average, people taking Mounjaro lost approximately 15–21% of their body weight over 72 weeks, alongside a reduced-calorie diet and exercise. However, these trials were not PCOS-specific populations. Real-world experience from UK GPs and weight management specialists suggests similar or sometimes greater benefit in PCOS patients, likely because insulin resistance is a key mechanism Mounjaro targets — but individual results vary considerably.
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Realistic Before-and-After Expectations
"Before and after" is a common way people think about weight loss, but it's important to understand what's realistic. Rather than focusing on dramatic appearance changes, the most meaningful outcomes are usually health improvements: lower blood pressure, better blood sugar control, reduced PCOS symptoms (like irregular periods or excess hair growth), improved fertility prospects, and increased energy and confidence.
Typical timeline: Most people on Mounjaro don't see noticeable weight loss until weeks 4–8, once the dose has been escalated. Peak weight loss typically occurs around 16–20 weeks, with continued gradual loss up to 72 weeks. After that, weight loss plateaus unless the dose is increased or lifestyle changes deepen. Track your progress using our free progress tracker to see your personal journey clearly.
Weight loss with Mounjaro is not assured, and stopping the medication typically leads to weight regain if lifestyle changes have not been sustained. This is why Mounjaro is always prescribed alongside dietary and exercise support — it's a tool to help you implement sustainable changes, not a replacement for them.
- 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 available on the NHS for PCOS?
NICE has approved tirzepatide (Mounjaro) for NHS use, but access is limited to specialist tier 3/4 weight management services. Eligibility requires a BMI of 30 or above (or 27+ with weight-related health conditions), which many PCOS patients meet. However, NHS waiting lists are very long in many regions. Your GP can refer you to your local specialist service, or you can access Mounjaro privately through a UK-licensed prescriber.
Can Mounjaro help with PCOS symptoms beyond weight loss?
Yes, potentially. Improved insulin sensitivity may help regulate menstrual cycles, reduce excess hair growth, and improve fertility prospects. Some people also report clearer skin. However, Mounjaro is licensed specifically for weight management, not as a PCOS treatment. Any improvements in PCOS symptoms are secondary to weight loss and improved insulin function. Your GP can advise on whether Mounjaro fits your individual PCOS management plan.
How much weight can I expect to lose on Mounjaro with PCOS?
Clinical trials showed average weight loss of 15–21% of body weight, but individual results vary significantly. With PCOS, outcomes can sometimes be better because Mounjaro targets insulin resistance specifically. However, there's no way to predict your personal result before starting. Use our GLP-1 weight loss calculator to see estimated outcomes at different doses, alongside your GP's assessment.
How is Mounjaro dosed, and how long does it take to work?
Mounjaro starts at 2.5mg once weekly, increasing by 2.5mg every 4 weeks up to a maximum of 15mg. Most people don't see significant weight loss until weeks 4–8 (after dose escalation). Peak weight loss typically occurs around 4–5 months in. Doses are adjusted based on tolerance and effectiveness — your prescriber will personalise this.
What are the main side effects, and do they improve?
The most common side effects are nausea, diarrhoea, and constipation (affecting over 1 in 10 people). Most improve after the first 2–4 weeks as the body adjusts, though some people experience ongoing nausea. Serious side effects are rare but include severe stomach pain (possible pancreatitis) — seek urgent medical attention if this occurs. Discuss individual risk with your prescriber.
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.