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 and Your Period — Cost and Access in the UK
Mounjaro (tirzepatide) is a prescription-only weight management injection that may affect your menstrual cycle, particularly during the first few months of treatment. If you're considering Mounjaro in the UK, it's important to understand both how it might impact your period and what costs to expect. This guide covers private prescription pricing by dose and explains the different routes to access Mounjaro through the NHS or private prescribers.
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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.
Private Mounjaro Costs by Dose in the UK
Private prescription costs for Mounjaro vary depending on the dose and your chosen provider. A typical Mounjaro KwikPen (4-week supply) costs approximately:
- 2.5 mg starting dose: £129–£160 per pen
- 5 mg dose: £149–£180 per pen
- 7.5 mg dose: £169–£200 per pen
- 10 mg dose: £189–£220 per pen
- 12.5 mg dose: £209–£240 per pen
- 15 mg maximum dose: £229–£260 per pen
Monthly costs typically range from £130–£260 depending on your dose escalation stage. An online clinical assessment is required before prescription (usually £15–£30). Prices vary between providers and may change. Always check current pricing with your chosen prescriber before starting treatment.
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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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NHS vs Private Access — What to Expect
NHS route: Mounjaro is available through NHS specialist weight management services (tier 3). You'll need a GP referral to access specialist assessment. Eligibility requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions. However, NHS availability varies significantly by region, and waiting lists can be lengthy in many areas—sometimes 6 months to over a year.
Private route: Online prescribers registered with the UK regulator can assess you and issue a prescription without NHS referral. You choose your dose schedule and receive your KwikPen directly. This provides faster access but requires upfront payment. If you're concerned about how Mounjaro dose titration might affect your menstrual cycle, a private prescriber can discuss this during your assessment and potentially adjust your timeline accordingly.
- 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.
Does Mounjaro affect your period?
Yes, Mounjaro may affect your menstrual cycle, particularly during the first few months as your body adjusts. Some women report delayed periods, lighter or heavier bleeding, or irregular cycles. These changes typically settle after a few months. If your period changes significantly or doesn't return to normal, contact your GP or prescriber. Mounjaro isn't recommended during pregnancy or breastfeeding.
How much does Mounjaro cost privately in the UK?
A single KwikPen (4-week supply) costs £129–£260 depending on your dose. Starting doses (2.5–5 mg) are at the lower end; higher doses approach £260. Monthly costs vary as you increase doses during titration. Add £15–£30 for your initial online clinical assessment. Prices may vary between providers.
Can I get Mounjaro free on the NHS?
Mounjaro is available on the NHS through specialist weight management services if you meet eligibility criteria and are referred by your GP. However, availability varies by region and waiting lists are often very long. Private prescription offers faster access but requires payment. Ask your GP about NHS routes first; they can advise on your local services.
Is there any difference between NHS and private Mounjaro?
No—the medication itself is identical. The difference is access speed, cost, and support. NHS provides free treatment but involves waiting and regional variation. Private prescribing is faster and doesn't require NHS referral, but you pay upfront. Both routes require a valid prescription from a UK-licensed prescriber.
What's the difference between Mounjaro and Wegovy for period health?
Both are prescription-only GLP-1-based medications that may affect your menstrual cycle. Mounjaro is a dual GIP/GLP-1 agonist; Wegovy is GLP-1 only. Mounjaro typically requires fewer injections (once weekly vs Wegovy's once weekly, but different dosing) and may offer faster average weight loss. Individual period impacts vary. Discuss side effects with your prescriber to find the right option.
Ready to take control of your weight loss journey?
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