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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Is Mounjaro Taken Every 5 Days?
Mounjaro (tirzepatide) is a prescription-only weight management injection taken once weekly, not every 5 days. Each dose should be separated by approximately 7 days, though the medication can be taken between 2 and 14 days from your last injection if needed. If you've missed a dose or are unsure about your dosing schedule, always contact your prescriber or pharmacist for guidance. Getting the timing right is important for consistent results.
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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.
Understanding Mounjaro's Weekly Dosing Schedule
Mounjaro is a once-weekly injection, meaning you take one dose every 7 days. Each KwikPen contains 4 doses — enough for 4 weeks of treatment. The standard schedule is to inject on the same day each week, such as every Monday morning.
If you need to adjust your injection day slightly, the medication allows some flexibility. According to prescribing guidance, you can take Mounjaro between 2 and 14 days from your previous dose without losing effectiveness. However, this flexibility is only for occasional adjustments — your regular schedule should remain as consistent as possible.
- Standard interval: 7 days (once weekly)
- Minimum interval: 2 days between doses
- Maximum interval: 14 days between doses
- Each KwikPen provides 4 weekly doses
- Consistency helps maintain steady medication levels
If you're considering changing your regular dosing day, speak with your prescriber first to ensure it's medically appropriate.
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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.
What to Do If You Miss a Mounjaro Dose
If you miss your regular Mounjaro injection, the action depends on how much time has passed. Within 4 days of your scheduled dose, take the injection as soon as you remember and continue with your normal weekly schedule from there. If more than 4 days have passed since your missed dose, skip that dose entirely and take your next injection on your normally scheduled day.
Never take a double dose to make up for a missed injection. If you're unsure whether to take a dose, contact your prescriber, pharmacist, or call NHS 111 for guidance. Missing occasional doses is unlikely to cause harm, but consistent adherence helps you get the best results from the medication. Use our free GLP-1 weight loss calculator to track your projected outcomes with regular dosing.
- 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 every 7?
No. Mounjaro is licensed for once-weekly dosing only. Taking it every 5 days would mean injecting more frequently than prescribed, which could increase the risk of side effects and is not medically recommended. Always follow your prescriber's instructions. If you're struggling with your current schedule, discuss alternatives with your GP.
What happens if I inject Mounjaro 2–3 days early?
If you inject 2–3 days early, you're still within the safe dosing window (2–14 days from the last dose). However, this shouldn't become routine. If you frequently need to adjust your schedule, speak with your prescriber about setting a more convenient injection day.
Is Mounjaro the same as Wegovy?
No. Mounjaro (tirzepatide) and Wegovy (semaglutide) are different medications with different mechanisms. Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy is a GLP-1 agonist only. Both are prescription-only and dosed differently — Mounjaro is once weekly, Wegovy is also once weekly but has a different dosing schedule and maximum dose.
Should I set a reminder for my Mounjaro injection day?
Yes. Setting a weekly phone reminder or calendar alert helps you stick to your schedule consistently. Many people choose the same day each week (such as Monday morning) to make it easier to remember. Consistency with your dosing schedule may help optimise results.
What if I'm 1–2 weeks late with my Mounjaro injection?
If you're 1–2 weeks late, you're still within the safe dosing window (up to 14 days). Take the dose as soon as you remember. If longer than 14 days has passed and your prescriber hasn't advised otherwise, contact them for guidance before injecting. Never guess — always ask if you're unsure.
Ready to take control of your weight loss journey?
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