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 taken as a once-weekly injection using a pre-filled KwikPen device. Each dose is given on the same day each week, making it convenient for most people. In the UK, Mounjaro is a prescription-only medicine available through both NHS specialist services and private online prescribing. Understanding how it works, what it costs, and how to access it is important before considering this treatment for weight management.
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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: The Weekly Injection Schedule
Mounjaro is administered once per week as a subcutaneous injection — meaning it's injected under the skin using the pre-filled KwikPen device. You choose the same day each week to take your dose, which helps build a routine and makes it easier to remember. Each KwikPen contains four weekly doses, so one pen lasts exactly four weeks before you need a new one.
The dose titration (escalation) process starts at 2.5 mg per week and increases gradually over several weeks. You remain on each dose for a minimum of four weeks before escalating to the next strength. The maximum dose is 15 mg once weekly. This gradual approach allows your body to adjust and helps minimise gastrointestinal side effects. You inject into your stomach (abdomen), upper thigh, or upper arm, rotating the injection site each week to prevent skin irritation.
- Week 1–4: 2.5 mg once weekly
- Week 5–8: 5 mg once weekly
- Week 9–12: 7.5 mg once weekly
- Continues up to 15 mg at maintenance
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.
UK Access Routes: Cost, NHS Eligibility & Private Options
In the UK, you can access Mounjaro through two routes: NHS specialist weight management services or private online prescribing. NHS access requires a GP referral to a tier 3 or tier 4 weight management service, but availability varies significantly by region and waiting lists can be very long. Private access is available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber.
Private costs vary by dose and provider, typically ranging from £129 to £320 per month depending on which dose you're on. NHS access is free at point of care, but regional variation means some areas have limited or no availability. Your GP can advise whether you meet NHS eligibility criteria (BMI 30+ or 27–29.9 with weight-related conditions) and discuss both routes with you. Use our GLP-1 weight loss calculator and BMI calculator to understand your starting point before consulting your healthcare provider.
- 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 injection?
Yes, Mounjaro (tirzepatide) is administered as a once-weekly subcutaneous injection using a pre-filled KwikPen device. You take it on the same day each week, making it straightforward to incorporate into your routine. Each pen contains four weekly doses.
How much does Mounjaro cost in the UK privately?
Private Mounjaro costs typically range from £129 to £320 per month depending on the dose strength you're on. The higher the dose, the higher the cost. Prices vary between different GPhC-registered private prescribing services, so it's worth comparing. Always ensure you're using a legitimate, regulated prescriber.
Can I get Mounjaro on the NHS in the UK?
Mounjaro is available through NHS specialist tier 3 and tier 4 weight management services, but access varies significantly by region. You'll need a GP referral and must meet eligibility criteria (BMI 30+ or 27–29.9 with weight-related conditions). Waiting lists can be lengthy in many areas.
What is the Mounjaro KwikPen and how do I use it?
The KwikPen is Mounjaro's pre-filled injection device. It's easy to use — you select your dose on the pen, inject subcutaneously into your abdomen, thigh, or upper arm, and rotate injection sites weekly. Each pen contains four weekly doses, lasting one month.
How does Mounjaro compare to Wegovy in terms of dosing?
Both are once-weekly injections, but they differ in dose ranges and mechanisms. Mounjaro is a dual GIP and GLP-1 agonist (2.5–15 mg weekly), while Wegovy is a GLP-1 agonist only (0.25–2.4 mg weekly). Your prescriber will assess which is more suitable based on your individual health 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.