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
Do You Take Mounjaro Once A Week?
Yes, Mounjaro is administered as a once-weekly injection. Each KwikPen contains four weeks' worth of doses, delivered subcutaneously (under the skin) every seven days. Unlike some weight management medications, tirzepatide only requires one injection per week, making it a convenient option for UK adults managing their weight. The dual GIP and GLP-1 mechanism works throughout the week, and you'll typically follow a dose escalation schedule starting at 2.5mg before potentially increasing to maintenance doses of up to 15mg weekly.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
Once-Weekly vs Daily: How Mounjaro Compares to Wegovy
Mounjaro is administered once weekly, whereas Wegovy (semaglutide) requires once-daily injections, making the injection frequency a key practical difference between these two GLP-1-based weight management treatments. The SURMOUNT clinical trial demonstrated that Mounjaro participants lost an average of 15–21% of their body weight at the maximum 15mg dose, achieved with once-weekly dosing. Wegovy, by contrast, is a GLP-1-only agonist (not dual GIP+GLP-1) and showed average weight loss of approximately 15% in STEP trials using once-daily administration. Beyond frequency, the core difference lies in mechanism: Mounjaro's dual receptor activation may explain slightly higher average weight loss in trials, though individual results vary considerably. Both are prescription-only and require a clinical assessment to determine which suits your personal health profile. Your prescriber will consider your eligibility, medical history, and lifestyle when recommending either option.
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.
Mounjaro Dosing Schedule and Injection Frequency
Mounjaro follows a structured dose titration schedule beginning at 2.5mg weekly for four weeks, then escalating every four weeks through 5mg, 7.5mg, 10mg, 12.5mg, and up to 15mg as the maximum therapeutic dose. Each UK KwikPen pen contains four weeks' supply (four individual injections), delivered pre-filled for ease of use. You inject at the same time each week—typically in the stomach, thigh, or upper arm. This consistent weekly rhythm differs from daily injections required by some weight loss treatments, potentially improving adherence. The once-weekly schedule also means less frequent needle contact and simpler routine integration. Our GLP-1 weight loss calculator can help you understand how dose escalation typically works and what timeline to expect on this medication.
- 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.
Is Mounjaro a once-weekly or daily injection?
Mounjaro is a once-weekly injection administered every seven days using a pre-filled KwikPen device. You inject the same dose at the same time each week, making it simpler than daily injection regimens. Each pen contains four weeks' supply.
How does Mounjaro's weekly schedule compare to Wegovy?
Mounjaro is once-weekly, while Wegovy is once-daily. Both are effective for weight management, but Mounjaro's lower injection frequency may be more convenient. Mounjaro uses a dual GIP+GLP-1 mechanism versus Wegovy's GLP-1-only action, though individual results vary and prescriber assessment determines suitability.
What happens if I miss a Mounjaro injection?
If you miss a dose within four days, take it as soon as you remember and continue your normal weekly schedule. If more than four days have passed, skip that dose and take your next injection on the scheduled day. Never take a double dose. Always check the patient information leaflet or contact your pharmacist for specific guidance.
Can I adjust when I take my weekly Mounjaro injection?
Yes, you can change your injection day if needed, but maintain a consistent once-weekly rhythm with at least 72 hours (three days) between doses. Discuss any schedule changes with your prescriber or pharmacist to ensure continuity of treatment and avoid missed doses.
Does the once-weekly dosing of Mounjaro affect weight loss results?
The once-weekly administration is designed to maintain steady hormone levels throughout the week. Clinical trials (SURMOUNT) used weekly dosing and achieved average weight loss of 15–21%, though results depend on dose level, diet, activity, and individual factors. Your prescriber will tailor the dose to your needs.
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.