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 Dose for Weight Loss in the UK
Mounjaro (tirzepatide) is a prescription-only weekly injection for weight management available in the UK through NHS specialist services and private prescribing. The dose ranges from 2.5 mg to a maximum of 15 mg per week, with individual doses adjusted based on tolerance and response. Understanding how Mounjaro dosing works, the NHS eligibility criteria, and what you can expect at each dose level will help you make an informed decision about this weight loss injection. This guide explains the complete UK prescribing 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.
How Mounjaro Dosing Works in the UK
Mounjaro is given as a once-weekly injection via a pre-filled KwikPen device. Treatment begins at 2.5 mg and typically increases every 4 weeks in a process called dose titration. Each dose is maintained for a minimum of 4 weeks before escalation, allowing your body to adjust and your prescriber to assess tolerability and weight loss response.
- Weeks 1–4: 2.5 mg (starting dose)
- Weeks 5–8: 5 mg (first escalation)
- Weeks 9–12: 7.5 mg
- Weeks 13–16: 10 mg
- Weeks 17–20: 12.5 mg
- Week 21+: 15 mg (maximum dose)
In clinical trials (SURMOUNT-1), participants at the 15 mg dose achieved an average weight loss of approximately 20.9% of body weight over 72 weeks, though individual results vary significantly. Some people reach their goal weight at a lower dose and may not need to escalate further. Your prescriber will personalise your dose titration based on your weight loss, side effects, and health goals.
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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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NHS Eligibility and Prescribing Routes in the UK
NHS access to Mounjaro is through tier 3 specialist weight management services, not routine GP prescription. You must be referred by your GP to a specialist multidisciplinary team in your local Integrated Care Board (ICB). Eligibility requires a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with a weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. Waiting lists for NHS services vary significantly by region and can take many months.
Private prescribing offers faster access through online consultations with UK-licensed prescribers. A clinical assessment determines suitability, and the prescription is dispensed by a GPhC-registered pharmacy. Private costs range from approximately £130–£320 per month depending on dose. Use our GLP-1 weight loss calculator to estimate potential weight loss outcomes at different doses, and the BMI calculator to check your current eligibility status.
- 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 for weight loss?
The starting dose is 2.5 mg once weekly. This introductory dose is used for the first 4 weeks to minimise side effects and allow your body to adjust. After 4 weeks, your prescriber will typically increase the dose to 5 mg if tolerated well. Dose increases continue every 4 weeks until you reach an effective maintenance dose or the maximum of 15 mg.
Can I stay on a lower Mounjaro dose if I am losing weight?
Yes. If you are achieving your weight loss goals at 5 mg, 7.5 mg, or 10 mg, there is no requirement to escalate to the maximum 15 mg dose. Your prescriber will personalise your treatment. Some people respond well to lower doses with fewer side effects. The goal is effective weight loss with acceptable tolerability for you individually.
How long does it take to see weight loss on Mounjaro?
Clinical trials showed meaningful weight loss starting around week 4–8, with progressive loss continuing through 72 weeks. Individual timelines vary. Some people notice appetite suppression within days of starting, whilst others take several weeks. Weight loss typically accelerates as you escalate doses. Consistency with diet and physical activity alongside the injection supports better outcomes.
What is the difference between Mounjaro and Wegovy dosing?
Mounjaro (tirzepatide) starts at 2.5 mg and goes up to 15 mg weekly, whilst Wegovy (semaglutide) starts at 0.25 mg and goes up to 2.4 mg weekly. Mounjaro is a dual GIP/GLP-1 agonist; Wegovy is a GLP-1 agonist only. Both are once-weekly injections. Average weight loss at maximum dose is similar (approximately 15–21% for Mounjaro, 15% for Wegovy), but individual responses differ.
Will my NHS GP prescribe Mounjaro, or do I need a specialist?
Mounjaro for weight management is prescribed by tier 3 specialist weight management services, not routine GP practice. Your GP can refer you to your local specialist service, but access depends on your local ICB commissioning and waiting list availability. Private prescribing through online consultations is an alternative route that does not require NHS referral and often has shorter timescales.
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