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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Can I Take Mounjaro Every Other Week for Weight Loss?
No, Mounjaro is designed as a once-weekly injection and should not be taken every other week without explicit guidance from your prescriber. The standard UK prescribing protocol involves weekly injections with a minimum of 72 hours between doses. Taking Mounjaro less frequently than prescribed can reduce its effectiveness and may affect your weight loss results. Your GP or specialist will assess the right dose and frequency for your individual health needs through the NHS tier 3 weight management service or private prescription route.
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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.
How Mounjaro Dosing Works in the UK
Mounjaro is a once-weekly weight loss injection that must be administered on a consistent schedule. The standard UK prescribing guidance requires patients to inject once every 7 days, with a minimum gap of 72 hours (3 days) between doses. The KwikPen device contains 4 weeks' worth of doses, with each pen delivering 4 injections.
The dose titration schedule typically involves:
- Weeks 1–4: 2.5 mg (starting dose)
- Weeks 5–8: 5 mg (first maintenance dose)
- Weeks 9–12: 7.5 mg (if needed)
- Weeks 13+: Escalation to 10 mg, 12.5 mg, or maximum 15 mg
Clinical trials like SURMOUNT-1 demonstrated weight loss outcomes based on consistent weekly dosing. Taking Mounjaro every other week would fall outside this evidence base and could compromise results. Your prescriber may adjust your dose, but not the weekly frequency, unless there are specific clinical reasons documented in your NHS or private 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 to Do If You Miss a Dose
If you miss a Mounjaro injection, NHS and private guidance advise:
- Within 4 days of the missed dose: Take it as soon as you remember, then continue your normal weekly schedule
- More than 4 days late: Skip that dose and take your next injection on your normal day
- Never take a double dose to make up for a missed injection
The 72-hour minimum gap between injections is a safety guideline—intentionally spacing doses further apart (such as fortnightly) is different from occasionally missing a dose. If you're struggling to manage a weekly schedule or have concerns about frequency, discuss this with your GP or the prescriber who issued your prescription. They may suggest practical solutions or, in rare cases, consider alternative treatments if weekly injections are genuinely not feasible for you.
- 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 every 10 days instead of every 7 days?
No. Mounjaro must be taken once weekly (every 7 days) according to UK prescribing guidelines. Taking it every 10 days falls outside the licensed dosing schedule and evidence base. The minimum interval between doses is 72 hours, but the standard frequency is weekly. If you have concerns about timing, speak to your GP or prescriber—they can adjust your dose, but not the weekly frequency.
What if I accidentally took Mounjaro 3 days early instead of on my usual day?
If you've taken an injection fewer than 7 days after your last one but more than 72 hours, you should be fine. The 72-hour minimum gap is the safety threshold. Return to your normal weekly schedule from that new date. If you have concerns, contact your GP or pharmacist for reassurance.
Does Mounjaro work the same if I space doses further apart?
No. Clinical trials (SURMOUNT-1) were based on consistent weekly dosing. Spacing doses further apart (such as every 10–14 days) would likely reduce effectiveness and weight loss results. Mounjaro is designed to maintain steady hormone receptor activation through regular weekly injections. Altering the frequency without medical approval is not recommended.
Is Mounjaro available through the NHS for weight loss, and what's the prescribing pathway?
Yes, Mounjaro (tirzepatide) is NICE-approved and available through NHS specialist tier 3 weight management services for eligible adults with a BMI of 30 kg/m² or above, or 27–29.9 with weight-related health conditions. However, NHS access is limited by regional availability and waiting lists. You can also obtain Mounjaro privately via a UK-licensed prescriber following an online clinical assessment.
What's the difference between the standard Mounjaro schedule and Wegovy for weight loss injections?
Both Mounjaro and Wegovy are once-weekly weight loss injections licensed in the UK. Mounjaro is a dual GIP and GLP-1 receptor agonist (doses from 2.5 mg to 15 mg), while Wegovy is a GLP-1 receptor agonist only (doses from 0.25 mg to 2.4 mg). Both must be taken weekly. Clinical trials showed average weight loss of around 15–21% with Mounjaro and approximately 15% with Wegovy, though individual results vary significantly. Your prescriber will assess which is most suitable for you.
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.