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 Dosage in the UK — NHS Prescribing Guide
Mounjaro (tirzepatide) is a prescription-only GLP-1 receptor agonist and GIP receptor agonist approved by the MHRA for weight management in UK adults. It's dispensed as a once-weekly injection via a KwikPen device. Understanding how Mounjaro dosage works, from starting dose through to maintenance, is essential if you're considering this treatment. The NHS may prescribe Mounjaro through specialist tier 3 weight management services, though availability varies significantly across regions. This guide explains UK dosing protocols, how doses are escalated, and what to expect at each stage of treatment.
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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 Dosage Works in UK Treatment
Mounjaro is administered as a once-weekly injection, with doses increasing gradually over approximately 20 weeks. Treatment begins at a 2.5 mg starting dose for the first four weeks, then progresses through escalation doses of 5 mg, 7.5 mg, 10 mg, and 12.5 mg, before reaching the maximum maintenance dose of 15 mg once weekly. Each dose must be held for at least four weeks before escalation — your prescriber will assess your response and tolerability at each stage. The KwikPen device contains four doses (one month's supply), and each pen is pre-filled and ready to use. You'll inject under the skin once per week on the same day each week, rotating injection sites between your abdomen, thigh, and upper arm. Your GP or specialist prescriber may keep you on a lower maintenance dose if that provides effective weight loss with manageable side effects — not everyone needs to reach 15 mg.
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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 Mounjaro Prescribing and Eligibility
Access to Mounjaro on the NHS in the UK is managed through specialist tier 3 weight management services, not routine GP prescription. Your GP can refer you to these services if you meet eligibility criteria: a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or sleep apnoea. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply. However, NHS availability is extremely limited in many regions, with waiting lists of several months to years. Many patients access Mounjaro through private prescribing pathways following an online clinical assessment, which avoids NHS waiting times. Your prescriber will assess your suitability, medical history, and current medications before issuing a prescription.
- 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 is the starting dose of Mounjaro in the UK?
The starting dose is 2.5 mg once weekly, held for four weeks. This allows your body to adjust. After four weeks, your prescriber will assess your response and may escalate to 5 mg. Gradual escalation helps minimise nausea and other side effects commonly experienced during the first weeks of treatment.
How long does it take to reach the maximum Mounjaro dose?
It typically takes approximately 20 weeks to reach the 15 mg maintenance dose if you escalate at each four-week interval. However, many patients achieve effective weight loss at lower doses (5 mg, 7.5 mg, or 10 mg). Your prescriber may pause escalation if you're seeing good results and tolerating the medication well.
Can I stay on a lower Mounjaro dose if it's working?
Yes. Not everyone needs 15 mg. If you're losing weight consistently and managing side effects well at a lower dose like 7.5 mg or 10 mg, your prescriber may recommend staying at that dose. Treatment is personalised based on your individual response and tolerability.
How do I get Mounjaro on the NHS in the UK?
NHS access is through specialist tier 3 weight management services following referral from your GP. You must meet eligibility criteria (BMI 30+, or 27–29.9 with comorbidities). Availability varies significantly by region. Many patients access Mounjaro privately following an online clinical assessment to avoid long NHS waiting lists.
What happens if I miss a Mounjaro dose?
If you miss your injection, 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 regular day. Never inject a double dose. Maintain at least 72 hours between doses to stay safe.
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.