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 Every 5 Days — UK Dosing Information
Mounjaro is prescribed as a once-weekly injection in the UK, not every 5 days. The standard dosing interval is exactly 7 days — the same day each week. If you're considering adjusting the interval between your Mounjaro KwikPen injections, it's essential to speak with your prescriber first. This guide explains the approved UK dosing schedule, eligibility criteria, and why maintaining the correct interval matters for safety and effectiveness.
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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.
UK Mounjaro Dosing Schedule and Safety
Mounjaro's licensed dosing in the UK is once every 7 days (weekly), not every 5 days. The tirzepatide prescription specifically requires one injection per week on the same day. Your prescriber will advise you to inject on the same day each week — for example, every Monday — to maintain consistent blood levels of the medication.
- Standard interval: exactly 7 days between doses
- Missed dose window: if you miss your dose, take it within 4 days of the scheduled time, then resume your regular weekly schedule
- Minimum time between doses: at least 72 hours (3 days) if doses must be rescheduled
- Do not inject more frequently than once weekly — this could increase side effects and isn't supported by clinical evidence
The SURMOUNT clinical trials, which led to Mounjaro's UK approval, tested the once-weekly dosing schedule. Changing this interval without medical guidance could affect how the medication works and increase risks. Always contact your prescriber if you need to adjust your injection schedule.
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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 Eligibility for Mounjaro in the UK
In the UK, Mounjaro is available through both NHS specialist tier 3 weight management services and private prescribing routes. NHS access requires a referral from your GP to a specialist weight management service, though availability varies significantly by region and waiting lists can be lengthy.
Eligibility typically includes: a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes or hypertension. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply. Whether accessing Mounjaro via the NHS or privately, your prescriber will assess your individual health and confirm the standard weekly dosing schedule is safe for you. Use our free BMI calculator to check your personal BMI and eligibility context.
- 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.
Can I take Mounjaro every 5 days instead of weekly?
No. Mounjaro is licensed in the UK for once-weekly dosing only. Taking it every 5 days would be off-label and not supported by clinical evidence. Always follow your prescriber's instructions. The once-weekly schedule was tested in the SURMOUNT trials and is the only approved dosing interval.
What if I accidentally miss my weekly Mounjaro dose?
If you miss your dose, take it within 4 days of your scheduled injection day, then return to your normal weekly schedule. If more than 4 days have passed, skip that dose and take your next scheduled dose as planned. Minimum spacing between doses is 72 hours.
Why is Mounjaro prescribed weekly and not more frequently?
The once-weekly dosing is based on the drug's pharmacology and how long it remains active in your body. The SURMOUNT clinical trials tested this schedule, and it provides consistent therapeutic benefit without requiring daily injections. Weekly dosing also improves medication adherence.
Is the dosing schedule different if I'm accessing Mounjaro via NHS vs private prescription?
No. Regardless of whether you access Mounjaro through an NHS specialist service or private prescribing, the dosing schedule is the same — once weekly. All UK prescribers follow MHRA-approved guidance. Your prescriber may adjust your dose amount (2.5 mg up to 15 mg) but not the frequency.
What happens if I want to change my injection day?
You can change the day of the week you inject, but it should still be once every 7 days. For example, you can move from Monday to Friday if it suits your schedule better. Contact your prescriber before making changes, and ensure at least 72 hours pass between your last injection and your new scheduled day.
Ready to take control of your weight loss journey?
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