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 Weight Loss Doses in the UK
Mounjaro (tirzepatide) is a prescription-only, once-weekly injectable weight loss medication now available through NHS specialist services and private prescribing in the UK. Understanding the correct dosing schedule is essential — Mounjaro uses a stepped dose escalation plan rather than a fixed dose. Your dose will typically increase every 4 weeks, starting at 2.5mg and potentially reaching 15mg per week. This guide explains the complete NHS-approved dosing schedule, eligibility criteria under NICE guidance, and what to expect during your treatment journey.
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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.
Mounjaro Dose Schedule and Escalation
Mounjaro follows a structured dose titration schedule, meaning your dose increases gradually over time. Each dose is administered once weekly via the KwikPen auto-injector device.
- Weeks 1–4: 2.5mg (starting/adjustment dose)
- Weeks 5–8: 5mg (first maintenance dose)
- Weeks 9–12: 7.5mg (escalation)
- Weeks 13–16: 10mg (escalation)
- Weeks 17–20: 12.5mg (escalation)
- Week 21+: 15mg (maximum maintenance dose)
Each KwikPen contains four doses (four weeks' supply). You remain on each dose for a minimum of 4 weeks before increasing. Your prescriber may keep you at a lower dose if you experience side effects or if weight loss goals are met. The dose escalation is not mandatory — your healthcare provider will assess whether to progress based on your individual response and tolerance.
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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.
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NHS Access, NICE Approval, and Eligibility
NICE has approved tirzepatide (Mounjaro) for weight management within NHS specialist services, though access varies significantly by region. Most NHS prescriptions come through tier 3 specialist weight management services, which typically involve waiting lists. Under NICE guidance, you may be eligible for NHS Mounjaro if you have a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or cardiovascular disease.
If NHS waiting times are lengthy in your area, private online prescribing provides faster access. Private routes require an online clinical assessment with a UK-licensed prescriber and cost approximately £150–£300 monthly depending on your dose. Use our free BMI calculator and weekly weight loss injection projection tool to understand your current position and potential outcomes with different doses.
CLINICAL CONTEXT: In the SURMOUNT-1 trial, participants on 15mg Mounjaro lost an average of 20.9% of their body weight over 72 weeks — though individual results vary significantly. Weight loss was achieved alongside reduced-calorie diet and increased physical activity. Your prescriber will discuss realistic expectations based on your starting weight, lifestyle factors, and any medical conditions. Dose adjustments may be needed if you experience gastrointestinal side effects like nausea or vomiting, which are common during the first few weeks.
- 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 2.5mg once weekly. This is held for 4 weeks to allow your body to adjust. After 4 weeks, the dose typically increases to 5mg. Your prescriber may adjust the escalation plan based on your individual response and tolerance.
Can I stay on a lower Mounjaro dose if it's working?
Yes. Dose escalation is not mandatory. If you're experiencing good weight loss and managing side effects well at 5mg or 7.5mg, your prescriber may recommend staying at that dose rather than continuing to increase. The goal is effective weight loss with manageable side effects.
How long does it take to reach the maximum Mounjaro dose?
It takes approximately 20 weeks (5 months) to reach the maximum 15mg dose if you escalate every 4 weeks without interruption. However, many people remain on lower doses (5–10mg) and still achieve significant weight loss, which may be sufficient for your health goals.
Is Mounjaro available on the NHS in the UK?
Yes, NICE has approved Mounjaro for NHS use in specialist tier 3 weight management services. However, availability and waiting times vary significantly by region and ICB. Your GP can refer you to your local specialist service, though waiting lists can be several months. Private prescribing offers faster access through online assessment.
What happens if I experience side effects at my current Mounjaro dose?
Common side effects like nausea, diarrhoea, and constipation typically improve within 1–2 weeks. Your prescriber may recommend staying on your current dose for longer before escalating, or suggest practical strategies like dietary adjustments. In rare cases, dose reduction may be necessary if side effects are severe.
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.