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
Mounjaro Instructions PDF: NHS UK Prescribing Guide
If you've been prescribed Mounjaro (tirzepatide) in the UK, understanding how to use your KwikPen device correctly is essential for effective and safe treatment. This guide covers NHS prescribing context, dose instructions, storage requirements, and practical injection guidance. Mounjaro is a prescription-only, once-weekly injection licensed through the NHS for eligible adults with obesity or weight-related health conditions. Whether you've accessed it through NHS tier 3 specialist services or private prescribing, these instructions will help you manage your treatment confidently.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
NHS Mounjaro Prescribing and Dose Instructions
Mounjaro is available through two routes in the UK: NHS specialist weight management services (tier 3) or private prescribing. The NHS NICE guidance approves tirzepatide for adults with a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related comorbidities such as type 2 diabetes, hypertension, or cardiovascular disease. Ethnicity-adjusted thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults (BMI ≥27.5).
Mounjaro dose titration follows this standard NHS schedule:
- Weeks 1–4: 2.5 mg once weekly (starting dose)
- Weeks 5–8: 5 mg once weekly
- Weeks 9–12: 7.5 mg once weekly
- Weeks 13–16: 10 mg once weekly
- Weeks 17–20: 12.5 mg once weekly
- Week 21+: 15 mg once weekly (maximum maintenance dose)
Each dose remains for a minimum of 4 weeks before escalation. Your prescriber may adjust timing based on side effects or individual response. The injectable pen contains 4 doses (4 weeks' supply). Use our GLP-1 weight loss calculator to estimate potential outcomes at different dose levels.
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.
Mounjaro KwikPen Injection Instructions and Storage
Injection technique: Mounjaro is administered as a subcutaneous injection (under the skin) using the pre-filled KwikPen device. Rotate injection sites weekly between your stomach (abdomen), upper thigh, or upper arm (with assistance). Clean the injection site with an alcohol wipe and let it dry for 30 seconds. Inject at a 90-degree angle, hold for 3 seconds, then withdraw slowly. Never inject into areas with bruising, scarring, or tenderness.
Storage requirements: Unopened pens must be refrigerated at 2–8°C and kept in the original carton away from light. Do not freeze. After first use, pens can be stored at room temperature (below 30°C) for up to 30 days. Dispose of your pen after 30 days, whether or not it contains any remaining medication. Always check that your Mounjaro hasn't been frozen before use—if it has, discard it safely.
- 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.
Where can I get a Mounjaro prescription in the UK?
Through NHS tier 3 specialist weight management services (requires GP referral) or via private online prescribing from a UK-licensed prescriber. NHS access availability varies significantly by region and ICB. Private access is faster but involves prescription costs. Either route requires a clinical assessment confirming eligibility.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) activates GLP-1 only. Mounjaro's dual mechanism may produce slightly greater weight loss in clinical trials (~20.9% vs ~14.9% body weight at maximum dose). Both are once-weekly injections; individual response varies.
What should I do if I miss a Mounjaro injection?
If you remember within 4 days of the missed dose, inject as soon as you remember and resume your normal schedule the following week. If more than 4 days have passed, skip that dose and take your next injection on the regular day. Never double-dose. Minimum interval between injections is 72 hours.
Are there any drug interactions with Mounjaro?
Mounjaro may reduce absorption of oral medications, including oral contraceptives. Women using the pill should add a barrier method for 4 weeks after starting and after each dose increase. Diabetes medications (insulin, sulphonylureas) may need adjustment. Always inform your prescriber of all medications you take.
What side effects should prompt me to contact my GP?
Seek urgent medical attention for severe, persistent abdominal pain (possible pancreatitis), serious allergic reactions (facial swelling, difficulty breathing), vision changes, or signs of gallbladder problems. Common side effects like nausea and diarrhoea usually improve over time; discuss persistent effects 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.