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 5th Dose Syringe: UK Guide
The Mounjaro 5th dose syringe contains 15mg of tirzepatide, the maximum licensed dose available in the UK. This dose is reached after a structured 20-week titration process, with each KwikPen containing four weekly injections. Understanding when and why you reach the 5th dose, and what it means for your weight management journey with NHS or private prescription, helps you get the most from this prescription-only medication.
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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 Progression and the 5th Dose Step
Mounjaro is prescribed using a structured dose titration schedule designed to help your body adjust gradually. Each dose step lasts a minimum of four weeks, allowing your GP or prescriber to monitor how you respond before increasing further.
- Weeks 1–4: 2.5mg (starting dose)
- Weeks 5–8: 5mg (first escalation)
- Weeks 9–12: 7.5mg (second escalation)
- Weeks 13–16: 10mg (third escalation)
- Weeks 17–20: 12.5mg (fourth escalation)
- Week 21 onwards: 15mg (maximum dose — the 5th syringe)
The 5th dose syringe is the highest strength available, and most patients reach this dose between months 5 and 6 of treatment. Clinical trials, including NICE-reviewed data, showed that patients on the 15mg dose achieved weight loss of approximately 20.9% of their body weight on average, though individual results vary significantly. Your prescriber will assess whether continuing at 15mg or adjusting based on your response is appropriate for you.
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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.
Accessing Mounjaro's 5th Dose Through NHS or Private Prescription
In the UK, accessing Mounjaro to the 5th dose step depends on your route: NHS access is through tier 3 specialist weight management services following referral from your GP, with significant regional variation in availability and waiting times. Private access is through online clinical assessment with a UK-licensed prescriber, available without NHS referral but at personal cost. Both routes require your prescriber to confirm you've tolerated lower doses before progressing to 15mg. You can use our GLP-1 weight loss calculator to estimate potential outcomes at different doses, and discuss realistic expectations with your prescriber before reaching this maximum step.
- 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.
How many weeks does it take to reach the 5th dose (15mg) of Mounjaro?
It typically takes 20 weeks to reach the 5th dose of 15mg, as you spend a minimum of 4 weeks on each dose level. However, if your prescriber decides to hold you at a lower dose, you may not progress to 15mg. Your individual journey depends on how well you tolerate each dose and your health response.
What is the difference between Mounjaro's 15mg dose and lower doses like 10mg?
Clinical trial data showed that 15mg achieved average weight loss of approximately 20.9% of body weight, compared to about 19.5% at 10mg. The difference is modest but measurable. However, individual results vary significantly, and some people achieve excellent results at lower doses whilst tolerating side effects better.
Can I get the 5th dose Mounjaro syringe (15mg) through the NHS?
Yes, Mounjaro including the 15mg dose is now approved by NICE for NHS specialist weight management services. However, access varies significantly by region and NHS availability. You'll need referral to a tier 3 service from your GP. Many areas have long waiting lists, so private prescription may be quicker.
Is the 5th dose syringe (15mg) the maximum strength available?
Yes, 15mg is the maximum licensed dose of Mounjaro (tirzepatide) in the UK. Your prescriber will not escalate beyond this dose, though they may keep you at a lower dose if 15mg isn't tolerated well or isn't necessary for your health goals.
What should I do if I experience side effects at lower doses before reaching 15mg?
Tell your prescriber immediately. Some people experience nausea, diarrhoea, or stomach pain at lower doses. Your prescriber may hold you at the current dose longer, reduce to a previous dose, or stop treatment entirely. Never adjust doses yourself — always follow prescriber guidance.
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.