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
Free tracker included with every download this week
Can I Take Two 2.5mg Mounjaro Doses Together?
No, you should not take two 2.5mg Mounjaro doses together, and doing so would not follow UK prescribing guidelines. Mounjaro is a once-weekly injection, and the standard titration schedule requires staying on each dose for a minimum of 4 weeks before increasing. If you're concerned about your current dose or weight loss progress, discuss this directly with your GP or prescriber who can review your individual treatment plan and adjust your tirzepatide dosing appropriately within NHS NICE guidance.
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Calculate Your BMI Instantly
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 Titration and UK Prescribing Standards
Mounjaro (tirzepatide) follows a strict once-weekly dosing schedule in the UK. The standard dose titration protocol requires you to stay on each dose for a minimum of 4 weeks before your prescriber considers increasing it. This allows your body to adjust and helps your healthcare team assess how effective the current dose is for you.
- Weeks 1–4: 2.5mg (starting dose)
- Weeks 5–8: 5mg (first escalation)
- Weeks 9–12: 7.5mg
- Weeks 13–16: 10mg
- Weeks 17–20: 12.5mg
- Week 21+: 15mg (maximum)
Each Mounjaro KwikPen contains exactly 4 pre-filled doses (4 weeks supply) at the prescribed strength. Your prescriber determines the appropriate progression based on your weight loss response and how well you tolerate each dose. The minimum time between doses is 72 hours (3 days), but the standard schedule is 7 days apart.
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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.
Mounjaro vs Wegovy: Understanding Dose Differences
Mounjaro and Wegovy are different medications with different starting doses and maximum doses, so you cannot simply swap between them or take double doses of either. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that starts at 2.5mg and reaches a maximum of 15mg weekly. Wegovy (semaglutide) is a GLP-1-only medication that starts at 0.25mg and reaches 2.4mg weekly. Clinical trials showed Mounjaro produced slightly higher average weight loss (approximately 15–21% body weight) compared to Wegovy (approximately 15% body weight), but individual results vary significantly. Your prescriber will recommend which medication suits your specific health profile based on your eligibility, NHS NICE guidance, and your medical history — not dose amount.
- 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 happens if I accidentally inject two Mounjaro doses in one week?
Contact your prescriber or NHS 111 immediately for guidance. Do not inject again until advised. Doubling your dose accidentally could increase your risk of side effects. Your prescriber may recommend monitoring or adjusting your next injection schedule depending on the timing. Always keep your prescriber informed of any dosing concerns.
How do I know if my Mounjaro dose is working?
Your prescriber will review your weight loss progress at each dose escalation (usually every 4 weeks). Weight loss typically becomes noticeable after 4–8 weeks on a consistent dose. Use our free GLP-1 weight loss calculator to track your projected weight loss at different doses, and log your actual progress with our progress tracker. Your prescriber may also consider factors like appetite reduction and side effect tolerability.
Can I stay on 2.5mg Mounjaro if it's working for me?
Yes, in some cases. Although the standard titration schedule increases doses, some people achieve good weight loss results at lower doses. Discuss this with your prescriber if you're losing weight steadily and tolerating 2.5mg well. Your prescriber can keep you on the dose that's effective for you if the clinical benefit justifies remaining there rather than escalating.
How long should I wait between Mounjaro doses?
Mounjaro is a once-weekly injection, so the standard interval is 7 days (or 168 hours). The minimum safe interval between doses is 72 hours (3 days) — so you could inject between days 4 and 7 if needed. However, staying with the 7-day routine helps maintain consistent blood levels. If you've missed a dose, speak to your prescriber about rescheduling.
Is Mounjaro available on the NHS, or is it private-only?
Mounjaro is NICE-approved for NHS use within tier 3 specialist weight management services, but NHS availability varies by region and waiting lists can be lengthy. Private UK prescriptions are available through GPhC-registered online pharmacies following a clinical assessment. Your GP can refer you to NHS services if you meet the BMI and health criteria, or you can pursue private prescribing independently.
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.