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
Can I Take 2.5 Mg Mounjaro Twice A Week?
No — Mounjaro (tirzepatide) is designed as a once-weekly injection and should only be taken once per week at the prescribed dose. Taking 2.5 mg twice weekly would mean injecting double the intended amount and is not approved by the MHRA or recommended by prescribers. Mounjaro follows a strict dose titration schedule, starting at 2.5 mg and increasing gradually over weeks under medical supervision. If you're considering changing how you take your Mounjaro, speak to your GP or the prescriber who issued your prescription before making any changes.
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Calculate Your BMI Instantly
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 injection — this is the approved dosing frequency in the UK. Each dose is delivered via a KwikPen prefilled device, and you inject the same dose every 7 days.
The dose titration schedule is strict and specific:
- Weeks 1–4: 2.5 mg once weekly (starting dose)
- Weeks 5–8+: 5 mg once weekly (if tolerated)
- Weeks 9–12+: 7.5 mg once weekly (if needed)
- Weeks 13–16+: 10 mg once weekly
- Weeks 17–20+: 12.5 mg once weekly
- Week 21+: 15 mg once weekly (maximum)
Your prescriber increases your dose gradually over at least 4 weeks at each step. This allows your body to adjust and helps manage side effects. Never increase your dose or change the frequency without medical guidance.
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.
Why You Shouldn't Change Your Mounjaro Schedule
Mounjaro's dosing schedule is based on clinical trial evidence and approved safety data. The MHRA (UK Medicines and Healthcare products Regulatory Authority) has approved tirzepatide specifically as a once-weekly dose. Taking 2.5 mg twice weekly would expose you to 5 mg per week without the medical supervision and gradual titration designed to assess your tolerability.
If you're experiencing side effects or feel the current dose isn't working, contact your prescriber rather than adjusting yourself. Your GP or specialist can assess your response and adjust your dose following the approved schedule — or may recommend stopping temporarily and restarting at a lower dose if needed. Changing your injection frequency or dose without medical approval could affect your safety and results.
- 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 should I do if I miss a Mounjaro injection?
If you miss your dose within 4 days, take it as soon as you remember and continue your normal weekly schedule. If more than 4 days have passed, skip that dose and take your next injection on the normally scheduled day. Never take a double dose or inject twice in one week to catch up.
Can I inject Mounjaro more frequently to lose weight faster?
No. More frequent injections or higher doses won't speed up weight loss safely. Clinical trials showed results using the standard once-weekly schedule. Faster dosing increases the risk of serious side effects and hasn't been tested or approved. Your prescriber controls the pace of dose increases.
Why does Mounjaro use dose titration instead of starting at the maximum dose?
Gradual dose increases allow your body to adjust and help manage nausea, diarrhoea, and other side effects. Starting at 2.5 mg lets your prescriber assess how you respond before increasing. This approach has been proven safe and effective in clinical trials.
What happens if I can't tolerate the 2.5 mg starting dose?
Tell your prescriber immediately. They may recommend staying on 2.5 mg longer, temporarily stopping, or switching to an alternative medication. Never reduce the dose yourself — adjustments must be made by your GP or specialist.
Is Mounjaro the same as Wegovy or semaglutide?
No. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Both are once-weekly UK-licensed weight loss medications but work differently. Your prescriber decides which is appropriate for you based on clinical assessment.
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.