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 Often Can You Take Mounjaro?
Mounjaro (tirzepatide) is taken as a once-weekly injection, making it a convenient prescription-only weight management treatment in the UK. Unlike some older weight loss medications, you inject Mounjaro just once per week on the same day each week. The dose starts low and increases gradually over several months—a process called dose titration—to help your body adjust. Your prescriber will determine the right dosing schedule for your individual needs following a clinical assessment.
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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 Titration Timeline
Mounjaro comes as a once-weekly injection in a pre-filled KwikPen device. Each pen contains 4 weeks' worth of doses. The standard titration schedule is:
- Weeks 1–4: 2.5 mg once weekly (starting dose)
- Weeks 5–8: 5 mg once weekly
- Weeks 9–12: 7.5 mg once weekly
- Weeks 13–16: 10 mg once weekly
- Weeks 17–20: 12.5 mg once weekly
- Week 21+: 15 mg once weekly (maximum dose)
Your prescriber may pause increases if you experience side effects or adjust your schedule based on your response. You must wait at least 4 weeks at each dose level before increasing. Our GLP-1 weight loss calculator can help you explore potential outcomes at different doses alongside your prescriber's guidance.
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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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Mounjaro vs Wegovy: Dosing Frequency Comparison
While Mounjaro is injected once weekly at higher doses, Wegovy (semaglutide) requires a longer titration with lower starting doses and reaches a maximum dose of 2.4 mg—significantly lower than Mounjaro's 15 mg. Both are prescription-only and require clinical assessment in the UK. Mounjaro uses dual GIP and GLP-1 receptor action, whilst Wegovy activates GLP-1 only. In clinical trials, Mounjaro achieved higher average weight loss (15–21% body weight) compared to Wegovy (approximately 15%), though individual results vary considerably. Your GP or prescriber will assess which option suits your health profile, NHS NICE guidance, and regional availability.
- 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 more than once a week?
No. Mounjaro is designed as a once-weekly injection only. Taking it more frequently would not be appropriate and could increase side effects. Your prescriber determines the right dose and timing for you. Never change your injection schedule without professional guidance.
What happens if I miss a Mounjaro dose?
If you miss a dose within 4 days, inject as soon as you remember and resume your normal weekly schedule. If more than 4 days have passed, skip that dose and inject on your normal scheduled day. Never double-dose or inject two doses close together—maintain at least 72 hours between injections.
How long does it take to reach the maximum Mounjaro dose?
The standard titration takes approximately 20–21 weeks to reach the maximum 15 mg dose, starting from 2.5 mg. You spend 4 weeks at each dose level. Your prescriber may speed this up or slow it down based on side effects and how your body responds. Some people stay on lower maintenance doses if they achieve their goals.
Is Mounjaro's once-weekly schedule easier than other weight loss injections?
Yes, once-weekly dosing is generally considered more convenient than daily injections. Saxenda (liraglutide), an older GLP-1 option, requires a daily injection, whereas Mounjaro and Wegovy are both once-weekly. This makes adherence easier for many patients, though individual preference varies.
Can my GP prescribe Mounjaro, or do I need a specialist?
Mounjaro is currently available through NHS specialist tier 3 weight management services following referral from your GP—NHS availability varies by region. Private prescribing is also available through online clinical assessments with UK-licensed prescribers. Regional NHS capacity is very limited, so many people access it privately while on NHS waiting lists.
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.