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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Can You Skip a Week of Mounjaro?
If you've missed a dose of Mounjaro (tirzepatide) or are wondering whether you can skip a week, the answer depends on timing. You can take a missed dose within 4 days of when you were supposed to inject it. If more than 4 days have passed, skip that dose and take your next one on your regular schedule. Missing doses can affect your weight loss progress and medication effectiveness, so consistency is important. This guide explains what to do if you miss a dose and how Mounjaro's dosing compares to Wegovy.
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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.
Mounjaro Missed Dose Guidance vs Wegovy Timing
Mounjaro (tirzepatide) missed dose rules: If you forget your weekly injection, you have a 4-day window to take it. Within 4 days of the missed dose, inject as soon as you remember, then resume your normal weekly schedule. If more than 4 days have passed, skip that missed dose entirely and take your next injection on your regularly scheduled day. Never take a double dose to make up for a missed one.
- Minimum interval between doses: 72 hours (3 days)
- Each Mounjaro KwikPen contains 4 doses (4 weeks of treatment)
- Consistent weekly dosing is important for optimal results
Wegovy (semaglutide) timing is similar: Both medications are once-weekly injections with comparable missed dose windows. The key difference is mechanism — Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy is a GLP-1 agonist only. Regardless of which medication you're prescribed, maintaining consistent weekly dosing supports steady appetite regulation and weight loss.
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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.
Staying on Schedule: Consistency Matters
Skipping doses or irregular dosing can disrupt your body's adaptation to the medication and may reduce its effectiveness. If you frequently forget your weekly injection, consider setting a recurring phone reminder for the same day each week, or ask your prescriber about alternative reminders. Your GP or online prescriber can advise you on the best timing to fit your routine — for example, some people inject on the same day they do their weekly shopping, or every Sunday morning.
If you have concerns about missing doses or experience side effects that make you want to skip a week, contact your prescriber rather than stopping on your own. They may adjust your dose, manage side effects, or discuss alternatives if Mounjaro isn't working for you.
- 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 skip more than one week of Mounjaro?
Skipping multiple weeks disrupts your treatment and may reduce effectiveness. Your body adapts to the consistent weekly dose, so gaps can affect appetite suppression and weight loss progress. Contact your prescriber to discuss how to resume safely if you've had an extended break.
Can I switch between Mounjaro and Wegovy if I keep missing doses?
Both are once-weekly injections, so switching medications won't solve timing issues. The real solution is setting up a routine or reminder system. Your prescriber can help you find the best injection day that fits your lifestyle — consistency is key to both medications working well.
Does a missed dose of Mounjaro affect my weight loss?
One missed dose within the 4-day window won't derail your progress if you take it promptly. However, repeated missed doses can reduce effectiveness over time. Our GLP-1 weight loss calculator can help you understand projected results with consistent, regular dosing.
Is there a Mounjaro KwikPen dose that's easier to remember?
All Mounjaro doses (2.5mg to 15mg) are once-weekly injections with the same timing requirements. Your prescriber determines your dose based on clinical assessment and your health. Set a fixed day each week — consistency matters more than which specific dose you're on.
What's the difference between tirzepatide and other weight loss injections for dosing?
Tirzepatide (Mounjaro) is once-weekly, similar to semaglutide (Wegovy). However, tirzepatide's dual GIP and GLP-1 mechanism may offer different appetite suppression patterns. Your prescriber will decide which medication suits your needs based on your BMI, health conditions, and individual suitability.
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.