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
Free tracker included with every download this week
Week 4 Mounjaro — Cost and Access in the UK
Week 4 of your Mounjaro course marks a key milestone — you're on the 2.5mg starting dose before moving to the 5mg maintenance dose. If you're considering Mounjaro (tirzepatide) in the UK, understanding how to access it and what it costs is essential. This guide explains both NHS and private routes, helping you make an informed decision about your weight management options. Use our free GLP-1 weight loss calculator to estimate potential outcomes with Mounjaro.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Prescription Costs and Access in the UK
Private Mounjaro costs vary depending on dose and provider. At week 4 on the 2.5mg starting dose, prices typically range from £129–£180 per KwikPen (one month's supply of four injections). As you progress to higher doses, costs generally increase — the 5mg dose ranges from £149–£220, and the maximum 15mg dose can cost £200–£320 per month.
Access through private channels requires an online consultation with a UK-licensed prescriber. This assessment evaluates your BMI, weight-related health conditions, current medications, and medical history to determine suitability. If approved, your prescription is dispensed by a GPhC-registered pharmacy and delivered to your home. No NHS referral is needed, making private access faster — typically available within 1–2 weeks of consultation. You can use our free BMI calculator above to check your starting point before your consultation.
- Costs shown are approximate and vary by provider and dose
- Private prescriptions offer faster access than NHS routes in most regions
- Payment is usually per-dose or per-month depending on the provider
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 Access vs Private: What You Need to Know
NHS access to Mounjaro is through specialist tier 3 weight management services, not standard GP prescription. You'll need a GP referral to your local specialist weight management service (availability varies significantly by ICB region). NICE has approved tirzepatide for NHS use, but waiting lists can extend from several months to over a year in many areas. Once accessed through the NHS, the medication itself is typically free, though you may face long delays.
Private access requires an online clinical assessment from a UK-licensed prescriber, usually completed within 24 hours. If approved, your Mounjaro KwikPen is dispensed within days. The main advantage is speed; the main disadvantage is ongoing cost. Compare this against NHS access by calculating your projected weight loss with our GLP-1 weight loss calculator — understanding potential outcomes helps justify the investment.
- 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.
How much does Mounjaro cost at week 4 in the UK?
Week 4 is the starting 2.5mg dose. Private costs typically range from £129–£180 per KwikPen (one month supply). Costs vary by provider and may include consultation fees. NHS access is free but requires specialist referral and involves longer waiting periods, sometimes months or years depending on your region.
Can I get Mounjaro on the NHS at week 4?
Yes, but only through specialist tier 3 weight management services following a GP referral. NICE has approved tirzepatide for NHS use. However, NHS availability varies greatly by region, and waiting lists are often very long. Private prescription routes offer much faster access if you can afford the cost.
What's the difference between NHS and private Mounjaro access?
NHS access is free but requires a GP referral and involves specialist assessment and potentially long waiting lists. Private access requires an online consultation with a UK-licensed prescriber, costs between £129–£320 monthly depending on dose, but is available within days. Both routes require clinical assessment before prescription.
Do I need a GP referral to get Mounjaro privately?
No. Private prescriptions require an online clinical assessment with a UK-licensed prescriber but do not require a NHS GP referral. The prescriber reviews your health history, weight, BMI, and any weight-related conditions to determine suitability, then issues a prescription if appropriate.
How does the dose titration schedule affect cost?
Mounjaro starts at 2.5mg (week 1–4) then escalates every 4 weeks: 5mg, 7.5mg, 10mg, 12.5mg, and finally 15mg. Each dose increase typically increases monthly cost. Private providers usually bundle all doses in packages, though some charge per-dose. Calculate your projected weight loss at different doses using our GLP-1 weight loss calculator to understand long-term cost implications.
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.