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
Best Time Of The Day To Take Mounjaro
There is no specific best time of day to take Mounjaro — you can inject at any time that suits your routine, as long as you stick to the same day each week. Mounjaro (tirzepatide) is a prescription-only, once-weekly injection licensed for weight management in the UK. What matters most is consistency: choosing a day and time you'll remember, and taking your injection at that same time each week. This guidance applies whether you're accessing Mounjaro through NHS specialist services or private prescription following a clinical assessment.
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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.
Timing And Consistency Guidance
Mounjaro works best when taken consistently at the same time each week, but the actual clock time is entirely up to you. You might inject on a Monday morning before breakfast, Sunday evening after dinner, or Wednesday afternoon — any time suits your lifestyle. What the clinical evidence shows is that regular, weekly dosing at predictable intervals keeps medication levels stable in your body, which supports the appetite and weight management effects.
Your Mounjaro KwikPen can be stored at room temperature (below 30°C) for up to 30 days after first use, so you have flexibility about where and when you inject — at home, at work, or anywhere private and clean. Many people choose a day that's easy to remember: payday, a specific weekday, or a weekend morning. Set a phone reminder for your chosen day and time, especially in the first few weeks, until the routine becomes automatic.
- Same day every week is key — don't skip days or double up
- Any time of day is fine — morning, afternoon, or evening
- Rotate injection sites each week (stomach, thigh, or upper arm)
- Room temperature storage gives flexibility for your routine
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.
Managing Your Weekly Injection Routine
Setting up a sustainable routine helps you stay on track with your Mounjaro dose titration schedule. Many people find it helpful to inject on the same day as another weekly habit — for example, Sunday evening with your weekly meal prep, or Friday morning as a weekend-kickoff ritual. This natural anchoring makes it easier to remember without relying solely on phone reminders.
If you accidentally miss your injection window by a few days, you can still take it — within 4 days of your scheduled day is acceptable. If you miss it by more than 4 days, skip that dose and resume your normal weekly schedule. Never inject two doses close together or double up to make up for a missed dose. Your prescriber will discuss your specific dose and any adjustments needed, and our free GLP-1 weight loss calculator can help you understand potential outcomes at your current dose level.
- 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.
Does Mounjaro need to be taken at a specific time?
No, Mounjaro has no required time of day. You can inject any time that suits you — morning, afternoon, or evening. Consistency is what matters: choosing the same day and approximate time each week keeps your medication levels stable and supports the effectiveness of your treatment.
Can I change my injection day if I want to?
Yes, you can change your injection day if needed. Simply pick a new day and inject then, then continue weekly from that new day onwards. There's no medical reason you must stick to a specific calendar day — consistency and one week between injections is what counts.
What if I miss my weekly Mounjaro injection?
If you miss your injection by less than 4 days, inject as soon as you remember and continue your normal weekly schedule from then. If more than 4 days have passed, skip that dose entirely and take your next dose on your normal scheduled day. Never take a double dose to catch up.
Is it better to take Mounjaro with or without food?
Food doesn't affect how Mounjaro works — it's an injection, not an oral medication, so it doesn't interact with digestion. You can inject whether you've eaten recently or not. Many people find injecting at consistent times around meals helps create a memorable routine.
Can I inject Mounjaro at different times each week?
While you technically can, consistency helps your body adjust and makes it easier to remember. Pick a regular day and time — even if it's just "every Sunday evening" — and stick to it. This regularity supports both the medical effectiveness and your ability to maintain your treatment routine long-term.
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.