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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How Long Between Mounjaro Doses?
The time between Mounjaro doses is strictly one week. Mounjaro is a once-weekly injection, meaning you inject exactly seven days apart for your entire treatment. Missing the timing slightly won't cause harm, but staying consistent with your weekly schedule helps the medication work most effectively. This guide explains the dosing interval, what to do if you miss a dose, and how the dose titration process works in the UK.
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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 Dosing Schedule and Timing
Mounjaro is administered as a once-weekly injection using a pre-filled KwikPen device. Each injection should be given exactly seven days after your previous dose. The dose titration schedule follows a specific pattern: you start at 2.5 mg for four weeks, then increase to 5 mg, 7.5 mg, 10 mg, 12.5 mg, and finally 15 mg (the maximum dose). You must remain on each dose for at least four weeks before your prescriber increases it. This gradual titration helps your body adjust and minimises side effects like nausea.
- Week 1–4: 2.5 mg once weekly
- Week 5–8: 5 mg once weekly
- Week 9–12: 7.5 mg once weekly (if escalating)
- Week 13+: Continue escalation or maintenance at your prescribed dose
Each KwikPen contains four doses, providing a four-week supply. You'll need to order a new pen before your current one runs out. Your prescriber will review your progress at regular intervals to decide whether to increase your dose, keep you at the same level, or occasionally reduce it if side effects become difficult to manage.
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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.
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Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Missed Doses and Private vs NHS Access in the UK
If you miss a Mounjaro dose, the timing of your next injection depends on how many days have passed. If it's within four days of your missed dose, inject as soon as you remember and continue your normal weekly schedule from that point. If more than four days have passed, skip the missed dose and take your next dose on your usual scheduled day — never double-dose to make up for a missed injection.
Access to Mounjaro in the UK varies significantly. NHS access requires referral to a specialist tier 3 weight management service and availability is limited by region. Private prescribing is available through UK-licensed prescribers via online consultation; you'll be assessed for eligibility, then a prescription is issued and dispensed by a GPhC-registered pharmacy. Private access is faster but costs typically range from £129–£320 monthly depending on your dose. Either route, your prescriber will establish your injection schedule and provide clear guidance on when and how to inject.
If you miss a Mounjaro dose, the timing of your next injection depends on how many days have passed. If it's within four days of your missed dose, inject as soon as you remember and continue your normal weekly schedule from that point. If more than four days have passed, skip the missed dose and take your next dose on your usual scheduled day — never double-dose to make up for a missed injection. Maintain at least 72 hours (3 days) between doses.
Use our free GLP-1 weight loss calculator to estimate potential outcomes at different Mounjaro doses, and try our BMI calculator to track your progress as you lose weight. Access to Mounjaro in the UK varies: NHS access requires specialist referral (availability varies by region), while private prescribing through UK-licensed prescribers offers faster access at a cost. Your prescriber will establish your exact injection schedule once you begin treatment.
- 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 is the exact time between Mounjaro injections?
Mounjaro should be injected exactly seven days (one week) apart. Each injection is a once-weekly dose. If you're a day or two off schedule it's usually fine, but aim for consistency. Your prescriber will give you a specific day each week to inject.
What happens if I miss a Mounjaro dose?
If you're within four days of your missed dose, inject as soon as you remember and resume your normal weekly schedule. If more than four days have passed, skip that dose and inject on your regular scheduled day. Never take a double dose. Always maintain at least 72 hours between injections.
How long do I stay on each Mounjaro dose?
You must remain on each dose for a minimum of four weeks before your prescriber increases it. The titration schedule runs: 2.5 mg (weeks 1–4), 5 mg (weeks 5–8), 7.5 mg, 10 mg, 12.5 mg, and 15 mg maximum. Your prescriber adjusts based on your progress and how you tolerate the dose.
Can I change my Mounjaro injection day each week?
It's best to inject on the same day each week for consistency, but the key is maintaining seven-day intervals. If you need to shift your injection day, discuss this with your prescriber or pharmacist — they can advise on how to adjust without disrupting your schedule.
How do I store Mounjaro between doses?
Unopened pens must be stored in a fridge at 2–8°C and kept in their original carton. After first use, a pen can be kept at room temperature (below 30°C) for up to 30 days. Never freeze Mounjaro. Dispose of your pen 30 days after first use, even if medication remains.
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.