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
How Many Days Between Mounjaro Doses?
Mounjaro (tirzepatide) is a prescription-only injection administered once every 7 days. Each dose should be taken at roughly the same time each week, with a minimum interval of at least 72 hours (3 days) between injections if you need to adjust your schedule. Understanding the correct dosing interval is important for getting the most benefit from this weight management medication. Always follow your prescriber's guidance on timing.
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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.
Standard Mounjaro Dosing Schedule
Mounjaro is a once-weekly injection, meaning you inject yourself every 7 days. Each pre-filled KwikPen contains 4 doses, providing a 4-week supply. The ideal approach is to pick the same day and time each week — for example, every Monday at 9am — to maintain consistency and avoid missing doses.
- Standard interval: 7 days between injections
- Minimum interval: 72 hours (3 days) between doses
- Maximum interval: If you miss a dose, take it within 4 days of the scheduled time
- Each KwikPen: Contains 4 weekly doses (4 weeks of treatment)
Consistency matters — varying injection times significantly can affect how your body responds to the medication. Your prescriber will discuss the best injection day and time for your lifestyle during your clinical assessment.
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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 if You Miss a Mounjaro Dose?
If you forget your weekly Mounjaro injection, the action depends on how long it has been:
- Within 4 days of missed dose: Take the injection as soon as you remember, then continue with your normal weekly schedule
- More than 4 days since missed dose: Skip that dose and take your next injection on the normally scheduled day
- Never double dose: Do not inject extra medication to make up for a missed dose
Set a weekly phone reminder to help prevent missed doses. If you're struggling to remember, discuss this with your GP or prescriber — they may suggest an injection day that aligns better with your routine. Use our free GLP-1 weight loss calculator to track your progress and stay motivated with your Mounjaro treatment plan.
- 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.
Can I take Mounjaro 3 days instead of 7 days apart?
No. Mounjaro must be taken once weekly (7 days apart). The minimum interval between doses is 72 hours (3 days) only if you need to adjust your schedule. Taking it more frequently than once weekly is not recommended and may increase side effects without improving results. Always follow your prescriber's guidance.
What happens if I take Mounjaro 6 days instead of 7 days?
A 1-day variation (6 days instead of 7) is unlikely to cause harm and may not significantly affect your treatment. However, aim for consistency — the 7-day interval is designed to maintain steady medication levels. If you're frequently off-schedule, discuss this with your prescriber.
Is it better to inject Mounjaro in the morning or evening?
There is no clinical evidence that morning or evening injections work differently. Choose a time that suits your routine and stick with it consistently. Many people prefer morning injections to help them remember, but the most important factor is taking it at the same time each week.
Can I move my Mounjaro injection day forward or backward by a few days?
Yes, you can adjust your injection day if needed, as long as the new day is at least 3 days (72 hours) away from your last injection and you then maintain consistency with the new day going forward. Discuss any schedule changes with your prescriber beforehand.
What is the full Mounjaro dose titration schedule?
Mounjaro starts at 2.5 mg weekly and increases every 4 weeks: Week 1–4 = 2.5 mg, Week 5–8 = 5 mg, Week 9–12 = 7.5 mg, continuing up to a maximum of 15 mg weekly. Each dose step takes 4 weeks minimum before escalating. Your prescriber will determine your dose progression based on your individual response and tolerance.
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.