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 Miss a Mounjaro Dose
If you're prescribed Mounjaro (tirzepatide) in the UK, knowing how to handle a missed dose is essential for maintaining your treatment plan. Missing a weekly injection doesn't necessarily mean restarting your course—there are clear NHS and prescriber guidelines on how to proceed safely. This guide explains what to do, how timing affects your next dose, and the cost implications of accessing Mounjaro privately in the UK where many patients currently seek treatment outside NHS specialist services.
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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 and Private Cost Context
If you miss your weekly Mounjaro KwikPen injection, the action you take depends on how long ago your dose was due. Within 4 days of your scheduled injection, you can take your dose as soon as you remember and continue 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 regular scheduled day—this prevents doubling up and maintains consistent drug levels.
- Missed dose within 4 days: inject as soon as you remember
- Missed dose more than 4 days ago: skip and continue normal schedule
- Minimum gap between doses: 72 hours (3 days)
- Never take a double dose to make up for a missed injection
In the UK, Mounjaro is available through NHS specialist tier 3 weight management services (where access is limited and variable by region) and through private GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. Private costs typically range from £129 to £320 per month depending on your current dose level and provider, making adherence to your schedule important to avoid wasting doses or disrupting your tirzepatide course.
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.
NHS vs Private Access: How to Get Mounjaro in the UK
NHS access: Mounjaro is approved by NICE for NHS specialist weight management services, but availability is extremely limited. You'll need a GP referral to tier 3 services, and many areas have waiting lists lasting months or years. NHS prescriptions cost the standard £9.65 per item.
Private access: Most UK patients currently access Mounjaro privately. An online consultation with a UK-licensed prescriber takes 10–15 minutes, reviewing your medical history and eligibility. If approved, your prescription is sent to a GPhC-registered pharmacy, and your Mounjaro KwikPen is dispatched—typically within 24–48 hours. You'll receive support on storage, injection technique, and dose escalation. Using our GLP-1 weight loss calculator can help you understand potential outcomes across different dose levels before starting treatment.
What to expect in a private online consultation: The prescriber will ask about your weight, height, medical history (especially diabetes, gallbladder issues, or kidney disease), current medications, and any previous weight loss attempts. They'll check your eligibility based on your BMI and health conditions. If suitable, the prescription is issued electronically to a pharmacy. You won't pay the prescriber directly—payment goes to the pharmacy. Always verify the pharmacy is GPhC-registered on the General Pharmaceutical Council website before ordering. Repeat prescriptions are typically managed through the same provider, with follow-up consultations every few months to monitor progress and adjust your dose safely.
- 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 cost difference between NHS and private Mounjaro in the UK?
NHS Mounjaro costs £9.65 per prescription through standard NHS charges. Private prescriptions cost £129–£320 per month depending on your dose and provider, though some offer bundle pricing or payment plans. NHS access is via specialist services only; private access is faster but at a cost. Many patients choose private because NHS waiting lists can exceed 18 months.
Can I switch between NHS and private Mounjaro prescriptions?
Yes, but you'll need to inform your prescriber of any changes. If you start privately and later gain NHS access, your prescriber can coordinate this. If you're on NHS and want to go private temporarily due to waiting times, inform your GP. Avoid overlapping prescriptions. Always discuss switching with your prescriber to ensure continuity and safe dose management.
What happens if I forget my Mounjaro injection for a week?
If you miss by more than 4 days, skip that dose and resume your normal schedule the following week. Don't double up. Mounjaro's effectiveness depends on consistent weekly dosing; a single missed dose usually won't derail your progress, but repeated missed doses may reduce weight loss outcomes. Set phone reminders for your injection day.
How long do Mounjaro KwikPens last once I open one?
An opened KwikPen can be stored at room temperature (below 30°C) for up to 30 days. After 30 days, discard it even if doses remain. Unopened pens must stay in the fridge at 2–8°C. Never freeze. This is important for cost planning—if you frequently miss doses or delay injections, you may waste doses, increasing your effective cost per month.
Is Mounjaro cheaper than Wegovy in the UK private market?
Both Mounjaro and Wegovy typically cost between £129–£320 per month at similar price points, though pricing varies by provider and dose level. Mounjaro reaches its maximum dose (15 mg) in fewer weeks than Wegovy (2.4 mg), so your escalation timeline and total months on treatment may differ. Compare providers rather than assuming one medication is always cheaper. Our weight loss calculator can help you compare potential outcomes at different doses.
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.