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 Injection Dose — What You Need to Know
Mounjaro (tirzepatide) is a prescription-only weekly weight loss injection available in the UK through NHS specialist services and private prescribing. The dose starts at 2.5mg and increases gradually over several months, with a maximum of 15mg per week. Each dose is delivered via a pre-filled KwikPen device. Understanding the dosing schedule, how your dose might increase, and NHS eligibility criteria is essential before starting treatment. This guide explains how Mounjaro dosing works in a UK context.
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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.
NHS Mounjaro Dosing and Eligibility in the UK
Mounjaro is administered as a once-weekly injection, with doses starting at 2.5mg and escalating to a maximum of 15mg per week. Your prescriber will typically keep you on each dose for at least 4 weeks before increasing, allowing your body to adjust and your prescriber to assess effectiveness and side effects.
- Weeks 1–4: 2.5mg (starting dose)
- Weeks 5–8: 5mg
- Weeks 9–12: 7.5mg
- Weeks 13–16: 10mg
- Weeks 17–20: 12.5mg
- Week 21+: 15mg (maximum dose)
In NHS specialist weight management services (tier 3), your GP will refer you if you meet eligibility criteria: BMI 30 or above, or BMI 27–29.9 with weight-related conditions (type 2 diabetes, hypertension, dyslipidaemia, or sleep apnoea). For South Asian, Chinese, Black African, or Black Caribbean adults, NHS thresholds start at BMI 27.5 or above due to higher metabolic risk in these groups. Clinical trials (SURMOUNT-1) showed average weight loss of 15–21% body weight on Mounjaro, though individual results vary significantly. Your prescriber will also assess your progress using our GLP-1 weight loss calculator and BMI calculator to monitor outcomes.
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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.
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 in the UK
NHS access: Available through tier 3 specialist weight management services following a GP referral. NICE has approved tirzepatide for NHS use, but availability and waiting times vary significantly by region and integrated care board (ICB). Some areas have waiting lists of several months to over a year.
Private access: A weekly weight loss injection can be prescribed through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. Private prescribing offers faster access without NHS referral, though costs apply (typically £129–£320 monthly depending on dose). Both routes require a prescription — Mounjaro cannot be obtained without clinical assessment. Use our BMI calculator to check your eligibility before consulting a prescriber.
- 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.
What's the difference between each Mounjaro dose?
Each dose (2.5mg, 5mg, 7.5mg, 10mg, 12.5mg, 15mg) is stronger than the last. Your prescriber increases your dose gradually to let your body adjust and minimise side effects. Not everyone needs to reach 15mg—some people achieve good results at lower doses.
How quickly does Mounjaro dose increase on the NHS?
On the NHS, dose increases typically follow a set schedule with at least 4 weeks between increases. This allows your prescriber to monitor your weight loss, side effects, and overall response. Dose escalation may be slower or paused if you're experiencing significant nausea or other side effects.
Can I stay on the same Mounjaro dose if it's working?
Yes. If you're losing weight steadily and tolerating the dose well, your prescriber may keep you at that dose rather than increasing further. The goal is effective weight loss with manageable side effects, not necessarily reaching the maximum dose.
What happens if I miss a Mounjaro injection?
If you miss a dose, take it within 4 days of the scheduled date and continue your normal weekly schedule. If more than 4 days have passed, skip that dose and take your next dose on the usual day. Never take two doses within 3 days.
Is Mounjaro dose the same on NHS and private prescriptions?
The dose and escalation schedule are the same whether prescribed by NHS or private prescribers—both follow MHRA-approved dosing guidance. The difference is access route, waiting time, and cost, not the medication or dosing protocol itself.
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.