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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What to Do If You Miss a Mounjaro Dose
Missing a Mounjaro injection happens — whether you've lost track of your schedule or faced an unexpected delay. The good news is you have a window of time to catch up without restarting your treatment. This guide explains exactly what to do, how long you have to take a missed dose, and how Mounjaro's missed dose guidance compares to Wegovy. Both are once-weekly GLP-1 and GIP/GLP-1 receptor agonist medications prescribed in the UK, but they have slightly different protocols.
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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 Guidelines — Step-by-Step
If you miss a Mounjaro injection, the action you take depends on how many days have passed since your scheduled dose:
- Within 4 days: Take your missed dose as soon as you remember. This keeps you on track with your weekly schedule.
- More than 4 days have passed: Skip the missed dose entirely. Take your next dose on your normal scheduled day — do not double dose.
- Minimum gap between doses: You must have at least 72 hours (3 days) between injections. Never inject more frequently than once weekly.
For example, if your normal injection day is Monday and you remember on Friday (4 days late), you can still take it. But if you remember on Saturday or later (5+ days), skip it and inject the following Monday as normal. Keep your KwikPen in the fridge between doses — storage affects reliability.
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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.
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Mounjaro vs Wegovy — Missed Dose Comparison
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are once-weekly weight loss injections licensed in the UK, but their mechanisms differ: Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy activates only the GLP-1 pathway. This difference affects how they work, but not significantly how missed doses are handled. Wegovy uses a similar 4-day grace period for missed doses. The key difference is their dose titration: Mounjaro starts at 2.5 mg and escalates to 15 mg maximum, while Wegovy starts at 0.25 mg and escalates to 2.4 mg. Clinical trials (SURMOUNT for Mounjaro and STEP for Wegovy) showed both support meaningful weight loss when used consistently with diet and exercise changes. Your prescriber will assess which is more suitable for your individual health.
- 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 a Mounjaro injection by a few days?
If you miss your injection within 4 days of your scheduled dose, take it as soon as you remember, then continue your normal weekly schedule. The 4-day window gives you enough time. Always ensure at least 72 hours between doses.
Can I take two Mounjaro doses close together to make up for a missed one?
No. Never double-dose or inject more frequently than once weekly. If you've missed more than 4 days, skip that dose and return to your normal schedule on your regular injection day.
Is the missed dose guidance different for Wegovy?
Wegovy uses a similar approach — if you miss within 4 days, take it as soon as you remember. Both medications require a minimum 72-hour gap between doses. Your prescriber can confirm exact timing specific to your treatment plan.
What should I do if I've lost my Mounjaro KwikPen or can't find it?
Contact your prescriber or pharmacy immediately — do not attempt to inject if you're unsure about the pen's integrity or storage. A replacement will need to be arranged. If you're close to your regular injection day, you may be advised to wait rather than adjust your schedule.
How does missing a dose affect my weight loss progress?
One missed dose is unlikely to significantly impact overall results, especially if caught within the 4-day window. Consistency matters most for sustainable weight loss. If you're struggling with adherence, discuss this with your prescriber — they can suggest strategies to help you stay on track.
Ready to take control of your weight loss journey?
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