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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When Should You Start Mounjaro? UK Cost & Access Guide
The best time to start Mounjaro depends on your individual health, eligibility, and whether you access it through the NHS or privately. Mounjaro (tirzepatide) is a prescription-only weight management injection available in the UK for adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. This guide covers UK costs, access routes, and what to expect when starting this dual GIP and GLP-1 agonist medication alongside lifestyle changes.
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Calculate Your BMI Instantly
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 Access and UK Mounjaro Costs
Private Mounjaro access in the UK typically costs between £129 and £320 per month depending on your starting dose and the provider. The standard starting dose is 2.5 mg (one KwikPen contains four doses), which usually costs around £129–£150 per month. Maintenance doses of 10 mg and 15 mg cost more, ranging from £220 to £320 per month. Unlike the NHS, private access does not require a GP referral to specialist weight management services — you can arrange a consultation directly with a UK-licensed prescriber through an online platform. Following your clinical assessment, if Mounjaro is deemed appropriate, a prescription is issued to a GPhC-registered pharmacy for dispensing. The entire process typically takes 5–10 days from consultation to receiving your first KwikPen. Many people choose private access to avoid NHS waiting lists, which can span months or years in some regions. Storage costs are minimal — you'll need refrigeration (2–8°C) for unopened pens, though opened pens can be kept at room temperature for up to 30 days.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
NHS vs Private: Which Route Is Right for You?
NHS access to Mounjaro is free at the point of use but requires referral to a specialist tier 3 weight management service. Your GP must refer you, and availability varies significantly by region and NHS integrated care board (ICB) funding decisions. Some areas have waiting lists of over 12 months. Once approved, NHS prescriptions cost nothing — you pay only the standard prescription charge (currently £9.90 in England, or free if eligible). Private access offers quicker availability and bypasses waiting lists but costs £129–£320 monthly. The choice depends on your urgency, financial capacity, and local NHS provision. Calculate your estimated weight loss using our free GLP-1 weight loss calculator to understand potential outcomes at different doses, which may help inform your decision. Check your BMI using our free BMI calculator — this determines eligibility for both NHS and private prescriptions.
- 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 cheaper on the NHS or privately in the UK?
NHS prescriptions are free (standard prescription charge only), but waiting lists can be 6–12+ months. Private prescriptions cost £129–£320 monthly but offer immediate access. NHS is cheaper long-term if you can wait; private is faster if cost is acceptable.
What's included in the monthly cost of private Mounjaro?
The monthly cost covers the KwikPen(s) only. You pay separately for the online clinical consultation (usually £30–£50), delivery, and any storage requirements. Subsequent months typically include only the medication cost and delivery.
How do I get a Mounjaro prescription privately in the UK?
Register with an online prescribing platform, complete a health questionnaire, have a consultation with a UK-licensed prescriber (video or telephone), and if approved, receive a prescription sent to a GPhC-registered pharmacy for dispensing within 2–5 business days.
Can I switch from private Mounjaro to NHS prescriptions?
Yes. If you're established on private Mounjaro and your GP refers you to an NHS specialist weight management service, you can transition to NHS prescriptions. Timing depends on local NHS availability and waiting lists.
What's the difference between starting Mounjaro and other weight loss injections like Wegovy?
Mounjaro is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is GLP-1 only. Clinical trials showed Mounjaro may support slightly higher average weight loss (~15–21% vs ~15% for Wegovy), though individual results vary significantly. Both are prescription-only and available via NHS or private routes in the UK.
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.