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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My Mounjaro Journey — What to Expect on the NHS
Starting Mounjaro through the NHS is a significant decision that involves understanding eligibility criteria, the prescribing pathway, and what the clinical evidence actually shows. This guide explains how Mounjaro (tirzepatide) works within NHS specialist weight management services, what NICE guidance says about its use, and how your personal journey might unfold from initial assessment through dose titration. Whether you're exploring whether you're eligible or already on treatment, understanding the NHS context helps you manage expectations and get the most from the support available.
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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.
NHS Eligibility and NICE Guidance for Mounjaro
NICE has approved tirzepatide (Mounjaro) for use within NHS specialist weight management services, but access is through tier 3 specialist services rather than standard GP prescription. You may be eligible if you have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² with at least one weight-related health condition such as type 2 diabetes, hypertension, or cardiovascular disease.
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply — eligibility may begin at BMI 27.5 or above, as these populations face higher metabolic health risks at lower BMI levels.
The tirzepatide approval is based on clinical trial data showing average weight loss of around 15–21% of body weight over 72 weeks when combined with lifestyle changes. However, individual results vary significantly — some people lose more, others less. Your GP can refer you to your local tier 3 weight management service, though waiting lists vary considerably across UK regions.
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 Routes — What's Different
If you access Mounjaro through the NHS, you receive specialist oversight, dietitian support, and psychological assessment as part of a structured programme. This typically involves more comprehensive health monitoring than private prescribing.
Private access is available through UK-licensed online prescribers and GPhC-registered pharmacies following a clinical assessment, without needing an NHS referral. This route is faster — you can usually start within days — but you manage your own ongoing care and costs range from approximately £129–£320 per month depending on dose.
Both routes require the Mounjaro KwikPen device (a pre-filled injection pen) and follow the same dose titration schedule, starting at 2.5 mg and increasing every 4 weeks if tolerated. Use our free GLP-1 weight loss calculator above to explore projected outcomes at different doses alongside your chosen pathway.
- 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 long does it take to get Mounjaro on the NHS?
NHS tier 3 services vary by region. Initial GP referral to specialist assessment typically takes 4–12 weeks in many areas, though some regions have longer waiting lists. Private prescribing is usually faster — initial consultation to first injection within 7–10 days. Your local integrated care board (ICB) can advise on current waiting times.
What's the difference between Mounjaro and Wegovy in NHS context?
Both are GLP-1-based weight loss injections licensed in the UK, but Mounjaro is a dual GIP/GLP-1 agonist while Wegovy is GLP-1 only. Clinical trials suggest Mounjaro may produce slightly higher average weight loss, though individual results vary. NICE has approved both. Your prescriber will assess which is appropriate for you.
Will my GP prescribe Mounjaro directly?
No — Mounjaro is not routinely prescribed in general practice. You must be referred to a tier 3 specialist weight management service by your GP. These services assess your eligibility, manage your clinical care, and oversee dose titration. Private online prescribers can issue prescriptions without NHS referral, but NHS access always goes through specialist pathways.
What happens during NHS Mounjaro dose titration?
You start at 2.5 mg once weekly for 4 weeks, then increase to 5 mg, 7.5 mg, 10 mg, 12.5 mg, and finally 15 mg — spending minimum 4 weeks on each dose. Your specialist team monitors your response, tolerability, and side effects at each step. Many people find their effective dose before reaching 15 mg. The whole process typically spans 5–6 months.
What side effects should I report to my NHS team?
Nausea, stomach pain, and diarrhoea are common early on and usually settle within weeks. Contact your NHS team urgently if you experience severe, persistent stomach pain (possible pancreatitis), serious allergic reactions, or gallbladder symptoms. Your specialist will adjust your dose or support strategy if side effects are limiting. Track your experience with our free progress tracker to discuss with your team.
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.