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
Your Pharmacist's Role With Mounjaro
Your community pharmacist plays a crucial role in your Mounjaro (tirzepatide) treatment journey. Whether you're accessing Mounjaro through the NHS specialist weight management service or via private prescription, your pharmacist is responsible for dispensing your medication, checking for safety concerns, explaining how to use your KwikPen device correctly, and monitoring for side effects. They're also your first point of contact for practical questions about storage, missed doses, and potential interactions with other medications you may be taking.
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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.
What Your Pharmacist Will Do When You Start Mounjaro
When you collect your first Mounjaro prescription, your pharmacist will:
- Verify the prescription is correctly issued by a UK-licensed prescriber
- Check your medical history for contraindications and drug interactions — especially important if you take oral contraceptives, diabetes medications, or other regular medicines
- Counsel you on storage (refrigerate unopened pens at 2–8°C; can be kept at room temperature below 30°C for up to 30 days after first use)
- Demonstrate how to use the KwikPen device safely, including injection technique and site rotation
- Explain common side effects (nausea, diarrhoea, constipation, stomach pain) and when to seek medical advice
- Discuss the importance of following your dose titration schedule (typically starting at 2.5 mg and escalating every 4 weeks)
Your pharmacist will also ask about your weight loss goals, dietary habits, and any previous experience with weight loss medications to provide personalised support.
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.
Ongoing Support and Safety Monitoring
Throughout your Mounjaro treatment, your pharmacist remains a key safety resource. They'll monitor for serious side effects such as severe, persistent stomach pain (possible pancreatitis), gallbladder problems, or allergic reactions — and advise you to contact your GP immediately if these occur. If you experience troublesome side effects like persistent nausea or vomiting, your pharmacist can suggest management strategies or recommend you speak with your prescriber about dose timing. They'll also track when you need repeat prescriptions, remind you about your dose escalation schedule, and check that your medication is being stored correctly. Many pharmacists now offer NHS medication reviews, where they assess whether your current medicines — including Mounjaro — are still appropriate for you. Use our free GLP-1 weight loss calculator to estimate potential progress, and discuss results with your pharmacist or prescriber at your next review.
- 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 my pharmacist prescribe Mounjaro?
No. Mounjaro is prescription-only and must be prescribed by a UK-licensed prescriber (GP, specialist doctor, or private online prescriber). Your community pharmacist cannot initiate treatment but will dispense it following a valid prescription and provide ongoing support and safety advice.
What if I have side effects from Mounjaro?
Tell your pharmacist immediately. Common side effects like nausea usually settle within days. For serious symptoms — severe stomach pain, allergic reactions, or changes in vision — contact your GP or call 111. Your pharmacist can suggest temporary management strategies and escalate concerns to your prescriber.
Can I take Mounjaro with my other medications?
Your pharmacist will check for interactions. Mounjaro may reduce absorption of oral medications, including oral contraceptives — inform your prescriber and pharmacist of all medicines you take. Your pharmacist will advise whether you need to adjust timing or switch contraception methods.
What happens if I miss a Mounjaro dose?
If you miss a dose within 4 days, take it as soon as you remember and continue your normal schedule. If more than 4 days have passed, skip it and resume your regular injection day. Never take a double dose. Discuss any concerns with your pharmacist.
Where should I get my Mounjaro prescription filled?
Any GPhC-registered UK pharmacy can dispense Mounjaro with a valid prescription. NHS prescriptions are free via your NHS weight management service. Private prescriptions can be dispensed at community pharmacies, hospital pharmacies, or online pharmacies — costs and availability vary by provider. ```
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.