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 I Take Mounjaro At Night Before Bed?
There's no specific restriction against taking Mounjaro at night before bed in the UK. Mounjaro (tirzepatide) is a once-weekly injection, and you can inject it any day and time that suits your routine — morning, afternoon, or evening. What matters most is maintaining a consistent weekly schedule. However, some people find that the timing of their injection may influence when side effects like nausea occur, so choosing a time that works for your lifestyle is important. Your prescriber can advise on the best timing for you personally. Use our free BMI calculator and GLP-1 weight loss calculator to understand your health baseline and explore potential outcomes with treatment.
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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 vs Wegovy — Timing and Injection Differences
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are once-weekly injections available by prescription in the UK, and both can be taken at any time of day, including before bed. The key difference lies in their mechanisms: Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways, while Wegovy is a GLP-1 agonist only. In clinical trials, Mounjaro (SURMOUNT-1) showed average weight loss of around 15–21% of body weight, while Wegovy (STEP-1) showed approximately 15% on average. Neither medication requires a specific injection time — consistency week-to-week matters far more than clock time. Some people prefer evening injections because they can rest if nausea occurs overnight, while others choose morning injections for convenience. The choice is yours, provided you maintain the same day each week and space injections at least 72 hours apart.
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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.
Practical Guidance — Choosing Your Injection Time
When deciding whether to inject Mounjaro before bed, consider your personal side effect pattern. Common side effects include nausea, constipation, and stomach discomfort — injecting in the evening allows you to sleep through early nausea if it occurs. You'll take Mounjaro using a KwikPen device, which is quick and simple. Store unopened pens in the fridge (2–8°C); after first use, you can keep the pen at room temperature for up to 30 days. Your prescriber will confirm the best timing for your UK prescription and dose titration schedule. Whichever time you choose, mark it in your calendar or set a phone reminder to stay consistent. Both medications require a UK prescription following a clinical assessment, and individual suitability depends on your personal health profile and eligibility.
- 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 any time of day?
Yes. Mounjaro is a once-weekly injection and can be taken morning, afternoon, or evening. What matters is that you inject on the same day each week, at least 72 hours apart from your previous dose. Timing within the day is your choice based on what suits your routine and side effect tolerance.
Is it better to take Mounjaro before bed or in the morning?
Neither is inherently better — it's personal preference. Some people prefer evening injections because nausea can be managed by sleeping through it. Others prefer mornings for ease of routine. Choose the time that fits your lifestyle, and stick with it consistently each week.
Does Wegovy have different timing rules than Mounjaro?
No. Wegovy is also a once-weekly injection with no specific time-of-day restriction. Like Mounjaro, you can take it any day and time — the key is weekly consistency. Both are injected subcutaneously (under the skin) on the same schedule pattern.
What's the main difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials showed Mounjaro users lost an average of 15–21% of body weight, while Wegovy users lost about 15%. Both require prescription and clinical assessment in the UK.
Can nausea from Mounjaro be worse at night?
Nausea timing varies individually — it's not necessarily worse at night. Some people experience nausea a few hours after injection regardless of timing. Taking Mounjaro before bed may help because you can sleep through mild nausea, but this is personal. Discuss side effect timing with your prescriber.
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.