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 Week by Week: Costs and Access in the UK
Understanding Mounjaro week by week helps you plan your weight management journey and know what to expect at each stage. Mounjaro (tirzepatide) is a prescription-only GLP-1 injection available in the UK through NHS specialist services or private prescription. This guide covers the dose titration schedule, typical costs, and how to access this medication both through the NHS and privately.
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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 Week by Week: Dose Titration Schedule
Mounjaro is prescribed as a dose titration schedule, meaning you start at a low dose and increase gradually over weeks. Week 1 begins with your first 2.5 mg injection—a starting dose to allow your body to adapt. You remain on this dose for 4 weeks (weeks 1–4). In weeks 5–8, you escalate to 5 mg, then weeks 9–12 move to 7.5 mg. The dose continues increasing in steps: 10 mg (weeks 13–16), 12.5 mg (weeks 17–20), and finally 15 mg (week 21 onwards) as the maximum maintenance dose. Each dose is a once-weekly KwikPen injection delivered as a pre-filled pen. Minimum 4 weeks at each dose means dose titration typically spans 5–6 months to reach maximum dose. Side effects like nausea and diarrhoea are often minimised by this gradual escalation. Clinical trials, including the SURMOUNT trial, showed that by week 72 (approximately 18 months), participants reached average weight loss of 15–21% body weight, though individual results vary significantly. The pace week by week allows your prescriber to monitor tolerance and adjust if needed.
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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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UK Costs and Access: NHS vs Private Routes
NHS access is through specialist tier 3 weight management services following GP referral—availability varies by region and waiting lists can extend many months. Private prescription routes are accessed through online consultations with UK-licensed prescribers; costs typically range from £129–£320 per month depending on dose and provider, with no pharmacy names disclosed here. An online clinical assessment takes 10–15 minutes and covers medical history, weight-related health conditions, and current medications. If approved, a prescription is issued electronically to a UK pharmacy. Private costs also include ongoing prescriber consultations (often £40–£80 per appointment). Using our GLP-1 weight loss calculator can help estimate potential outcomes, allowing you to assess whether the investment aligns with your goals. Both routes require genuine clinical need and assessment—prescription is not automatic.
- 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 often do I inject Mounjaro and for how long?
You inject once weekly, every 7 days. Treatment is ongoing—you don't stop after a set number of weeks. Most people continue as long as the medication is helping and side effects are manageable. Your prescriber will review your progress regularly and adjust if needed.
What is the cost difference between NHS and private Mounjaro in the UK?
NHS provision is free once approved through specialist services, but waiting lists are lengthy. Private prescription costs £129–£320 monthly depending on dose, plus prescriber consultation fees (typically £40–£80). Total private cost per month ranges £170–£400 initially.
Can I switch between NHS and private Mounjaro treatment?
Yes, you can move between routes, though continuity may be disrupted. If accessing through NHS, you'll stay within that pathway. Switching to private or vice versa requires a new clinical assessment. Your prescriber will advise on the safest transition.
What happens if I can't tolerate the dose increases week by week?
If side effects are severe, your prescriber may pause the dose increase or reduce back to a previously tolerated dose. Dose titration is flexible—there's no obligation to reach 15 mg. Many people find effective results at 10 mg or 12.5 mg.
How does Mounjaro compare to Wegovy in terms of week-by-week dosing and cost?
Mounjaro uses a dual GIP/GLP-1 mechanism and escalates from 2.5 mg to 15 mg over 5–6 months. Wegovy, a single GLP-1 agonist, escalates from 0.25 mg to 2.4 mg more rapidly (typically 16–20 weeks). Private costs are similar month-to-month, but Mounjaro may require fewer dose adjustments once stabilised.
Ready to take control of your weight loss journey?
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