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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Common Mounjaro Issues in the UK
Mounjaro (tirzepatide) is a prescription-only weight management injection licensed in the UK, but accessing it and managing it effectively requires understanding NHS pathways, eligibility criteria, and potential challenges. This guide covers the main issues UK patients face—from navigating tier 3 specialist services to managing side effects and understanding costs. Whether you're considering Mounjaro through the NHS or privately, knowing what to expect helps you make informed decisions about your weight management journey.
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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 Access and Eligibility Challenges
One of the biggest issues for UK patients is accessing Mounjaro through the NHS. NICE has approved tirzepatide for use within specialist weight management services, but availability varies dramatically by region and integrated care board (ICB). Many areas have extremely long waiting lists—sometimes 12 months or longer—meaning NHS access is often limited to those with significant comorbidities like type 2 diabetes or cardiovascular disease.
- You must be referred to a tier 3 or tier 4 specialist service by your GP—standard GP prescription is not available
- Eligibility requires a BMI of 30 kg/m² or above, or BMI 27–29.9 with weight-related health conditions
- For South Asian, Chinese, Black African, or Black Caribbean patients, lower BMI thresholds apply due to higher health risk at lower weights
- Once approved, dose titration takes 16–20 weeks before reaching the maximum 15 mg dose
Regional variation in NICE implementation means you may be eligible in one area but not another. Check your local ICB guidance or ask your GP about tier 3 services in your region.
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.
Managing Side Effects and Practical Issues
Side effects are the most common reason patients stop Mounjaro treatment. Nausea, diarrhoea, and constipation affect more than 1 in 10 users, particularly during dose escalation. These typically improve over 1–2 weeks but can be severe enough to impact daily life. Slower dose titration (staying at each dose longer) may help, but this requires prescriber approval and extends the treatment timeline.
- Gastrointestinal issues often settle as your body adjusts, but persistent problems should be discussed with your prescriber
- Hair loss (alopecia) has been reported during gradual weight management and may continue for months after stopping
- Injection site reactions are common but usually mild; rotating injection sites helps
- Some patients experience fatigue or dizziness, particularly in early weeks
Our GLP-1 weight loss calculator can help you understand projected outcomes and timelines, which may help set realistic expectations and reduce disappointment-related side effects.
- 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 available on the NHS in my area?
Mounjaro (tirzepatide) is NICE-approved for NHS use but availability depends on your integrated care board (ICB). Some areas have excellent access, others have waiting lists of 12+ months. Contact your GP or local tier 3 weight management service to ask about current availability and waiting times in your region.
What's the difference between NHS and private Mounjaro access?
NHS access requires GP referral to specialist services and depends on regional funding. Private access is faster (1–2 weeks) via online prescribing clinics but costs £150–£300+ per month depending on dose. Both routes require a clinical assessment; private prescribers are UK-licensed healthcare professionals.
How long does dose titration take on Mounjaro?
Dose titration typically takes 16–20 weeks. You start at 2.5 mg, then increase weekly (2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg). Some prescribers slow this if side effects are severe. The full dose is usually reached by week 20, though you may continue losing weight at lower doses.
Can I switch from Mounjaro to Wegovy or another medication?
Switching between GLP-1 or dual agonist medications is possible but must be managed by your prescriber. There is no official dose conversion chart—approximate equivalences exist (Mounjaro 15 mg ≈ Wegovy 2.4 mg), but individual responses vary. Always discuss switching with your healthcare provider before changing.
What happens if I stop taking Mounjaro?
Weight typically returns gradually after stopping, often returning to baseline within 6–12 months if lifestyle changes aren't maintained. Some weight loss benefits persist if you continue with reduced-calorie diet and exercise. Discuss stopping plans with your prescriber to minimise rapid weight regain.
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.