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
What Time of Day Should You Take Mounjaro?
Mounjaro (tirzepatide) is a once-weekly injection that you can take at any time of day that suits your routine. Unlike some medications, there's no specific time requirement — what matters most is consistency. You choose a day and time that you can reliably stick to each week, and you inject the same time every 7 days. This flexibility makes it easier to build the Mounjaro KwikPen injection into your weekly routine without disrupting your daily life.
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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.
Mounjaro Timing: UK Prescription Access and Costs
In the UK, accessing Mounjaro involves either the NHS specialist tier 3 weight management services or private prescription routes. NHS access is through referral to your local integrated care board's specialist weight management service — availability varies significantly by region, and waiting lists can be lengthy. Private access is available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. Private costs typically range from £129 to £320 per month depending on your current dose titration stage (starting doses cost less, maximum doses cost more). The Mounjaro vs Wegovy comparison often centres on cost — tirzepatide pricing is similar to semaglutide (Wegovy), though individual prescribers may vary pricing. Before any prescription is issued, you'll need to complete an eligibility assessment confirming your BMI and any weight-related health conditions.
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.
Getting Mounjaro in the UK: What to Expect
The online consultation process for private Mounjaro prescription is straightforward. You'll complete a health questionnaire, provide your height and weight (use our free weight converter if you need to switch between stone and kg), and answer questions about your medical history and any current medications. A UK-licensed prescriber reviews your information and decides whether Mounjaro is suitable for you. If approved, you receive a prescription, and the pharmacy dispenses your first KwikPen. You inject once weekly at your chosen time, increasing your dose gradually over several weeks as directed — your prescriber guides the dose titration schedule. Many people find setting a specific day helpful (e.g., every Monday morning) to maintain consistency and avoid missed doses.
- 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 at different times each week?
No — consistency is important. Choose a specific day and time each week and inject at the same time every 7 days. This helps you establish a routine and reduces the risk of missed or double doses. If you're more than 4 days late, skip that dose and resume your normal schedule the following week.
Does Mounjaro need to be taken with food?
No, Mounjaro injection timing is independent of meals. You can inject whether you've eaten or not. However, many people experience nausea as a side effect, so some find injecting before a light meal helpful. This is a personal preference — there's no clinical requirement either way.
What's the cost difference between Mounjaro and Wegovy on the NHS?
Both medications may be available through NHS tier 3 specialist weight management services, though Mounjaro (tirzepatide) is newer and availability varies by region. Costs to the NHS are similar, but regional ICBs (integrated care boards) set their own formularies. Private costs for both are comparable — around £129–£320 monthly depending on dose. Check your local NHS criteria and waiting times.
Should I inject Mounjaro in the morning or evening?
Either is fine — choose whichever fits your routine best. Morning injections help some people remember their weekly dose; others prefer evenings. The important thing is picking a consistent day and time you'll stick to. Many people use a phone reminder to avoid missed doses.
How long does a Mounjaro KwikPen last after opening?
Once you've injected the first dose, each KwikPen can be stored at room temperature (below 30°C) for up to 30 days. After 30 days, discard the pen even if doses remain. Unopened pens stay fresh in the fridge (2–8°C) until the expiry date printed on the carton.
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.