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 Skip A Week Of Mounjaro?
If you've missed a Mounjaro injection or are wondering whether you can skip a week, the answer depends on timing. The key rule is the 72-hour window. Mounjaro must be taken at least 72 hours (3 days) apart. Skipping an entire week isn't recommended without guidance from your prescriber, as it can disrupt your dose titration schedule and may affect how well the medication works. This guide explains the missed dose rules, what happens if you skip, and how to stay on track with your UK prescription.
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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 Rules And The 72-Hour Window
Mounjaro (tirzepatide) is a once-weekly injection that must be spaced at least 72 hours apart. If you miss a dose, the timing of when you realise determines what to do next.
- Within 4 days of your missed dose: Take the injection as soon as you remember, then continue your normal weekly schedule from that point.
- More than 4 days since your missed dose: Skip that dose and take your next injection on your normally scheduled day.
- Less than 72 hours until your next scheduled dose: Wait and take your next dose on schedule — do not take two doses close together.
The 72-hour minimum gap is a safety requirement. Never try to "catch up" by doubling up doses. Your prescriber will have explained your specific injection day when starting Mounjaro, so keeping to that day matters for consistency.
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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 Happens If You Skip A Week Of Mounjaro?
Intentionally skipping a full week is not recommended because Mounjaro works through consistent weekly dosing. If you skip a week, you may experience appetite control loss, reduced appetite suppression, or difficulty maintaining weight loss progress. Additionally, skipping doses can disrupt your dose titration schedule — the careful step-up from 2.5 mg through to your maintenance dose.
If you need to stop Mounjaro for any reason (travel, side effects, cost), speak to your prescriber first. They can advise whether a temporary pause is safe and how to resume safely. If cost is a barrier to staying on your UK prescription, discuss this openly with your GP or private prescriber — there may be alternatives or support available.
- 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's the 72-hour rule for Mounjaro injections?
Mounjaro must be injected at least 72 hours (3 days) apart. This is a safety requirement. You cannot inject two doses within 72 hours of each other. If your normal injection day is Monday, the earliest you could inject again is Thursday. Spacing prevents overdosing and helps your body respond consistently to the medication.
What if I miss my Mounjaro injection by 2 days?
If you miss your injection by up to 4 days, take it as soon as you remember. Then continue your normal weekly schedule from that point. For example, if you normally inject on Monday and inject on Wednesday instead, your next dose would be the following Tuesday (7 days after Wednesday). Don't wait to "get back" to Monday.
Can I skip a week of Mounjaro and then restart?
Skipping a full week is not recommended without guidance from your prescriber. Mounjaro requires consistent weekly dosing to maintain appetite control and weight loss support. If you need a break due to side effects, cost, or travel, speak to your prescriber first. They can advise on whether it's safe and how to resume safely without disrupting your dose titration.
What happens to my Mounjaro dose schedule if I keep missing injections?
Missing multiple injections will disrupt your dose titration schedule — the step-up from 2.5 mg to your maintenance dose. Your prescriber may need to restart or adjust your schedule. Consistency matters for safety and effectiveness. If you're struggling to stay on schedule, tell your prescriber — they may help problem-solve barriers like travel, cost, or side effects.
Is Mounjaro available on the NHS in the UK, or only private prescription?
Mounjaro is available through both NHS specialist tier 3 weight management services and private online prescribing following a clinical assessment. NHS access is through referral from your GP to a specialist service, though waiting times vary by region. Private prescription is faster but involves out-of-pocket costs. Your GP can discuss both routes.
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.