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 5mg — What You Need to Know
Mounjaro 5mg is the first maintenance dose of tirzepatide, a prescription-only weight management injection licensed in the UK. This guide explains how the 5mg dose works, UK eligibility criteria, what the NHS says, and how to access it through both NHS specialist services and private prescribing. If you're considering weight management treatment, understanding each dose is essential for informed decisions about your health.
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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 5mg Works in UK Weight Management
Mounjaro 5mg is typically reached after four weeks on the starting dose of 2.5mg. At this dose, tirzepatide activates dual GIP and GLP-1 receptor pathways, which work together to regulate appetite and support weight management. The dual mechanism may help reduce food cravings, support feelings of fullness after smaller meals, and slow how quickly food leaves the stomach.
In the SURMOUNT-1 clinical trial, participants on the 5mg dose achieved an average weight loss of approximately 15% of body weight over 72 weeks, alongside reduced-calorie diet and increased physical activity. However, individual results vary significantly — some people respond well at this dose, whilst others may need escalation to higher doses (7.5mg, 10mg, 15mg) for optimal results. Your prescriber will assess your progress and adjust accordingly.
- 5mg is the first maintenance dose after the initial titration phase
- Dual GIP/GLP-1 action sets it apart from single-action GLP-1 medications
- Clinical trial data shows meaningful average weight loss at this dose
- Minimum four-week commitment at this dose before escalation
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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 and UK Eligibility for Mounjaro
In the UK, Mounjaro is available through NHS specialist weight management services (Tier 3) for eligible adults, though access varies significantly by region and waiting lists can be lengthy. NICE has approved tirzepatide for NHS use, but prescribing is restricted to specialist tier 3/4 services — your GP cannot prescribe it directly.
NHS eligibility typically includes: BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. For South Asian, Chinese, Black African, and Black Caribbean adults, lower BMI thresholds apply (from 27.5). Private prescribing is also available through UK-licensed online services following a clinical assessment. Use our free BMI calculator to check your personal BMI and discuss options with your GP.
Mounjaro 5mg is typically well-tolerated, but common side effects include nausea, diarrhoea, vomiting, and constipation — usually mild and temporary. Most people adapt within a few weeks. Serious side effects are rare but include severe stomach pain (possible pancreatitis), gallbladder problems, or serious allergic reactions — seek immediate medical attention if these occur.
Before starting: Inform your prescriber of all medications, as Mounjaro may affect absorption of oral contraceptives and other oral medications. Women on oral contraceptives should add barrier contraception for four weeks after starting and after each dose increase. Your prescriber will conduct a full health assessment to ensure 5mg Mounjaro is safe for you personally.
- 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.
Is Mounjaro 5mg the maximum dose?
No. Mounjaro 5mg is the first maintenance dose. The maximum licensed dose is 15mg weekly. Most people stay at 5mg for at least four weeks before their prescriber considers escalation based on weight loss response and tolerance.
How long does it take to see weight loss results at 5mg?
Most people begin noticing changes within 2–4 weeks at the 5mg dose, though individual timelines vary. Clinical data shows average weight loss of approximately 15% body weight over 72 weeks at this dose, but results depend on diet, activity level, and individual metabolism.
Can I get Mounjaro 5mg on the NHS in the UK?
Yes, Mounjaro is NICE-approved for NHS use, but only through specialist tier 3 weight management services. Access and availability vary significantly by region and NHS waiting lists can be very long. Your GP can refer you, but prescribing happens in specialist services, not primary care.
What's the difference between Mounjaro 5mg and Wegovy?
Mounjaro is a dual GIP/GLP-1 agonist; Wegovy is a single GLP-1 agonist. Clinical trial data suggests Mounjaro may produce slightly higher average weight loss, but both are effective. Wegovy reaches 2.4mg maximum; Mounjaro escalates to 15mg. Individual response varies.
What should I do if I miss a Mounjaro 5mg injection?
If you remember within 4 days, inject as soon as possible and resume your normal weekly schedule. If more than 4 days have passed, skip the missed dose and inject on your normal scheduled day. Never take a double dose. Your prescriber can clarify your specific situation.
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.