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
What to Do if You've Missed Your Mounjaro Dose
If you've missed your Mounjaro injection, the action you need to take depends on how long it's been since your scheduled dose. Mounjaro (tirzepatide) is a once-weekly prescription medication, and missing a dose can affect your weight management progress. The good news is that a missed dose does not usually require an emergency call to your GP — but timing matters. This guide explains NHS guidance on missed doses and what to do next.
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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.
How to Handle a Missed Mounjaro Dose
Within 4 days of your missed dose: Take your Mounjaro injection as soon as you remember, then continue with your normal weekly schedule. For example, if you normally inject on a Wednesday and remember on Thursday or Friday, inject immediately and keep your next dose for the following Wednesday.
More than 4 days since the missed dose: Skip the missed dose entirely. Take your next injection on your normally scheduled day. Do not try to "catch up" with a double dose — this increases the risk of side effects and is not recommended.
Minimum spacing between doses: Ensure at least 72 hours (3 days) pass between injections. If you inject early to get back on schedule, make sure 3 days have passed since your last dose.
- Check your KwikPen to see when you last injected
- Set a phone reminder for your regular injection day
- Keep your prescriber informed if you frequently miss doses
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
When to Contact Your NHS Prescriber or GP
You don't need emergency medical help for a single missed dose of Mounjaro, but contact your prescriber if you have missed multiple doses in a row, if you're unsure whether you've taken a dose, or if you've experienced a serious side effect since your last injection. Your GP or NHS specialist weight management service can advise on dose timing and help you establish a routine to prevent future missed doses. If you're receiving Mounjaro through NHS tier 3 weight management services, your prescriber can provide additional support with adherence — this is an important part of NHS weight management care.
- 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 miss one Mounjaro dose?
A single missed dose will not cause immediate harm, but it may affect your weight management progress. If you remember within 4 days, take it as soon as you can. If more than 4 days have passed, skip the dose and continue your normal schedule. Contact your prescriber if you're unsure.
Can I take a double dose of Mounjaro to catch up?
No. Never take a double dose to make up for a missed injection. This increases the risk of side effects like nausea, vomiting, and stomach pain. Continue with your regular weekly schedule as planned.
What's the minimum time between Mounjaro injections?
You must leave at least 72 hours (3 days) between doses. Mounjaro is designed as a once-weekly injection — injecting too close together is not recommended and may increase side effects without improving results.
Should I call my GP if I miss a Mounjaro dose?
A single missed dose does not require an emergency call. However, contact your GP or NHS prescriber if you've missed multiple doses, are unsure whether you've injected, or have questions about your schedule. Your prescriber can help you establish a routine.
How can I avoid missing future Mounjaro doses?
Set a phone reminder for your regular injection day each week. Use our free progress tracker to log your doses and track your weight loss journey. Store your KwikPen properly in the refrigerator and mark your calendar. If you're on NHS Mounjaro through tier 3 services, your prescriber can offer additional support.
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.