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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Using Mounjaro for Weight Management With PCOS
Polycystic ovary syndrome (PCOS) often makes weight management difficult due to insulin resistance and hormonal imbalances. Mounjaro (tirzepatide) is a prescription-only injection that may help support weight loss alongside lifestyle changes. This guide explains how Mounjaro works, PCOS eligibility criteria, and how to access it through the NHS or private prescribing in the UK. Always consult your GP before starting any weight management medication.
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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 Works With PCOS
Mounjaro is a dual GIP and GLP-1 receptor agonist — this dual action makes it distinct from other weight loss injections like Wegovy (semaglutide), which activates only GLP-1. The medication works by helping to regulate appetite, reducing food cravings, and supporting a feeling of fullness after smaller meals. For people with PCOS, this mechanism may be particularly helpful because PCOS is characterised by insulin resistance, which contributes to weight gain and difficulty losing weight. While Mounjaro is not a diabetes medication, its dual action on glucose regulation alongside appetite suppression may offer additional benefits for those managing PCOS-related metabolic challenges. Mounjaro is administered as a once-weekly injection using a pre-filled KwikPen device. Doses range from 2.5 mg (starting dose) up to 15 mg (maximum dose), with escalation every 4 weeks. Clinical trials showed that participants using the highest doses lost an average of approximately 20.9% of body weight — though individual results vary significantly and depend on lifestyle changes, genetics, and overall health. Weight loss is not assured and must be combined with a reduced-calorie diet and increased physical activity for best results.
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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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PCOS, Eligibility, and NHS Access
PCOS itself is recognised as a weight-related health condition that may support eligibility for prescription weight loss treatment in the UK. You may be eligible for Mounjaro if you have a BMI of 27 kg/m² or above with PCOS (or other weight-related conditions), or a BMI of 30 kg/m² or above regardless of comorbidities. NHS access: Mounjaro is available through NHS tier 3 specialist weight management services — this means referral from your GP to a specialist centre. Availability varies significantly by region, and waiting lists can be lengthy. Private access: Mounjaro is also available through UK-licensed private prescribers following an online clinical assessment. A prescriber will evaluate your medical history, current medications (especially if you take hormonal contraception, which may have reduced absorption), and overall health before issuing a prescription. Our free GLP-1 weight loss calculator can help you explore projected weight loss at different Mounjaro doses — though actual results are individual.
- 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 specifically for PCOS?
No, Mounjaro is a general weight management injection licensed for adults with BMI 30+ or 27+ with weight-related conditions. PCOS qualifies as a weight-related condition, making Mounjaro potentially suitable. However, it is not PCOS-specific — it works on appetite regulation and metabolic pathways relevant to anyone seeking weight management support.
Does Mounjaro affect hormonal contraception?
Yes — Mounjaro may reduce absorption of oral contraceptives. NHS guidance recommends using a barrier method or switching to a non-oral contraceptive for 4 weeks after starting Mounjaro and 4 weeks after each dose increase. Discuss contraception options with your prescriber or GP.
Can I use Mounjaro if I'm trying to get pregnant?
No. Mounjaro is not recommended during pregnancy or if you are planning to become pregnant. If you are using Mounjaro and want to conceive, stop the medication and discuss family planning with your GP or specialist fertility service.
How long does it take to see weight loss results with Mounjaro?
Most people begin noticing appetite reduction within the first 1–2 weeks. Measurable weight loss typically becomes apparent after 4–8 weeks, though this varies. Sustained weight loss develops over months of consistent use alongside diet and physical activity changes.
What is the difference between Mounjaro and Wegovy for PCOS?
Mounjaro is a dual GIP+GLP-1 agonist; Wegovy is a GLP-1-only agonist. Clinical trials suggest Mounjaro may produce slightly greater weight loss on average, though both are effective. Choice between them depends on individual response, prescriber recommendation, and availability. Your healthcare provider can advise which suits your circumstances better.
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.