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 5 mg Injection — First Maintenance Dose Explained
Mounjaro 5 mg is the first standard maintenance dose for adults prescribed this weekly weight loss injection in the UK. It's used after a 4-week starting period on the 2.5 mg starter dose. This dose represents the point where most patients begin their ongoing treatment, though some may need escalation to higher doses over time. The 5 mg dose is delivered once weekly via a pre-filled KwikPen injector. Understanding how this dose works, who it suits, and what to expect can help you make informed decisions about weight management with your GP or prescriber.
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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 5 mg Works and What to Expect
Mounjaro is a dual GIP and GLP-1 receptor agonist — unlike simpler weight loss injections, it activates two natural hormone pathways simultaneously. At the 5 mg dose, this mechanism helps regulate appetite, reduce food cravings, and create a feeling of fullness after smaller meals. The injection slows how quickly food leaves your stomach, though this effect typically becomes less pronounced over time. Mounjaro 5 mg is a weekly injection meaning you take one dose every seven days using a pre-filled KwikPen device. In clinical trials (SURMOUNT-1), patients on 5 mg averaged approximately clinically studied weight loss over 72 weeks, though individual results vary significantly. This dose is prescription-only and requires a clinical assessment before being prescribed. Our free weight loss calculator can help you estimate potential results at different doses, though your actual outcomes will depend on your individual response, diet, and physical activity levels.
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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.
Eligibility, Dosing Schedule, and Side Effects
In the UK, eligibility for Mounjaro 5 mg includes adults with 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. The dose escalation schedule is strict: you remain on 2.5 mg for weeks 1–4, then move to 5 mg from week 5 onwards. Your prescriber may increase you to 7.5 mg or higher depending on your response and tolerance. Common side effects at 5 mg include nausea, diarrhoea, constipation, and reduced appetite — most mild to moderate and often improve over time. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and gallbladder complications. Access to Mounjaro in the UK is through NHS specialist tier 3 weight management services or private online prescribing following a clinical assessment. Use our BMI calculator above to check whether you may meet the eligibility criteria, and discuss Mounjaro with your GP or a licensed prescriber.
- 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 5 mg the highest dose I can take?
No. 5 mg is the first maintenance dose, not the maximum. Your prescriber may increase you to 7.5 mg, 10 mg, 12.5 mg, or 15 mg (the maximum) depending on your response and tolerance. Each dose increase requires a minimum of 4 weeks at the previous dose. Your prescriber decides the best escalation path for you.
How quickly will I lose weight on Mounjaro 5 mg?
Weight loss varies significantly between individuals. In clinical trials, the average loss on 5 mg was approximately 15% of body weight over 72 weeks. However, some people lose less, and some lose more. Results depend on your starting weight, diet, physical activity, genetics, and how your body responds to the medication. Track your progress with our free progress tracker.
Can I get Mounjaro 5 mg through the NHS?
Yes, but access is limited to NHS specialist tier 3 weight management services. Your GP must refer you, and you'll need to meet strict eligibility criteria. Waiting lists vary by region and can be very long. Private online prescribing is available as an alternative without an NHS referral, though there is a cost.
What happens if I miss a weekly injection?
If you miss a dose and remember within 4 days, take it as soon as possible and continue your normal schedule. If more than 4 days have passed, skip the missed dose and take your next injection on the normally scheduled day. Never take a double dose. Always contact your prescriber if you're unsure.
How does Mounjaro 5 mg compare to Wegovy?
Mounjaro is a dual GIP + GLP-1 agonist, while Wegovy is a GLP-1 agonist only. Clinical trials show Mounjaro may produce slightly higher average weight loss (~15–21% vs ~15%), but individual results vary. Both are prescription-only weekly injections. Your prescriber will advise which suits you based on your medical history and response.
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.