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 You Take Mounjaro Twice A Week?
No — Mounjaro is designed and prescribed as a once-weekly injection only. Taking tirzepatide twice a week is not recommended and is not part of the UK licensed dosing schedule. Each Mounjaro KwikPen contains enough medication for one injection per week over four weeks. If you're considering changing your dosing schedule, always speak to your GP or the prescriber who gave you the prescription first. This guide explains how Mounjaro dosing works in the UK and what to do if you have questions about your treatment.
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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 injection — this is the only licensed and recommended dosing frequency in the UK. Each dose is given exactly seven days apart, and the medication is designed to work within this weekly cycle.
- Starting dose: 2.5 mg once weekly for weeks 1–4
- Escalation doses: increased every 4 weeks if needed (5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg)
- Maintenance: most people reach an effective dose and continue with that same dose each week
- Each KwikPen contains 4 weekly doses — one injection per pen per week
The once-weekly schedule allows your body to adjust to each dose before increasing. Changing the frequency without medical guidance could affect how the medication works and increase the risk of side effects. If you're struggling with your current dose or injection schedule, contact your prescriber to discuss options — they may adjust the dose, not the frequency.
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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 Have Dosing Questions
If you're considering taking Mounjaro more frequently, this suggests your current dose may not be meeting your needs or you may have practical concerns about the weekly schedule. Always speak to your prescriber before making any changes. They can help by: adjusting your current dose upward within the licensed range, discussing any side effects you're experiencing, addressing practical concerns about timing or injection days, or exploring whether Mounjaro remains the right choice for you.
You can also track your progress using our free GLP-1 weight loss calculator to see projected outcomes at your current dose — this can help you have a more informed conversation with your prescriber about whether a dose adjustment might help.
- 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 three or four days instead of weekly?
No. Mounjaro must be taken once weekly — every seven days. Taking it more frequently is not supported by clinical evidence and could lead to excessive medication exposure. Any changes to dosing frequency require prescriber approval.
What if I miss my weekly Mounjaro injection?
If missed within 4 days, take it as soon as remembered and return to your normal weekly schedule. If more than 4 days have passed, skip that dose and take your next dose on the usual day. Never double-dose or take two doses close together.
How long does one Mounjaro injection last?
One 2.5–15 mg Mounjaro injection lasts for seven days. The medication is designed to be active throughout that week before the next dose is due. This is why the once-weekly schedule is essential for consistent results.
Is Mounjaro dosing different on the NHS compared to private prescription?
No. The licensed dosing schedule is the same whether prescribed through NHS specialist services or private prescription — once weekly, starting at 2.5 mg and titrating every 4 weeks as needed. Your prescriber will follow the same UK guidelines.
What's the difference between Mounjaro and Wegovy dosing frequency?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are once-weekly injections in the UK. Mounjaro is a dual GIP/GLP-1 agonist, while Wegovy is a GLP-1 agonist only. Neither should be taken more frequently than once weekly. Use our free BMI calculator and GLP-1 weight loss calculator to understand which might suit your needs — your prescriber can advise on the best option 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.