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
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Mounjaro Starter Bundle: UK Prescribing and Access
A Mounjaro starter bundle refers to the initial 2.5 mg dose used when beginning tirzepatide treatment in the UK. This is the standard starting point for all adults, regardless of their target dose, as NHS guidance and MHRA recommendations specify a gradual dose escalation approach. Understanding what's in your starter package, how the titration schedule works, and your eligibility through NHS or private routes will help you prepare for treatment. Use our free BMI calculator to check your personal BMI and understand your eligibility baseline before consulting your GP or a prescriber.
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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.
NHS Eligibility and Starter Dose Schedule
Who qualifies for Mounjaro on the NHS? Adults with a BMI of 30 kg/m² or above, or BMI of 27–29.9 with weight-related health conditions (type 2 diabetes, hypertension, dyslipidaemia, sleep apnoea, or cardiovascular disease) may be eligible. South Asian, Chinese, Black African, and Black Caribbean adults qualify at slightly lower BMI thresholds (from 27.5 kg/m²) due to higher health risks at lower weights. The starter dose is 2.5 mg once weekly for weeks 1–4. This is prescribed as a Mounjaro KwikPen (pre-filled pen with 4 doses). Your prescriber will assess suitability during a clinical consultation. NHS access is through specialist tier 3 weight management services via GP referral, with significant regional variation in availability and waiting times.
- Weeks 1–4: 2.5 mg once weekly (starter dose)
- Weeks 5–8: Increase to 5 mg (first escalation)
- Weeks 9+: Further increases possible to 7.5 mg, 10 mg, 12.5 mg, or 15 mg maximum
- Minimum 4 weeks on each dose before escalation
Each KwikPen contains exactly 4 weekly doses. Your GP or NHS specialist will determine your escalation schedule based on individual response and tolerability.
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.
NHS vs. Private Access Routes in the UK
NHS route: Referral to a tier 3 specialist weight management service is required. Your GP assesses suitability and refers you. Once accepted, the NHS specialist team prescribes and monitors your treatment, including dose adjustments and side effect management. This is free at point of use but waiting lists can be several months in many regions. Private route: You can access a private online prescription without NHS referral by consulting a UK-licensed prescriber through a GPhC-registered pharmacy. The clinical assessment is done online, and if approved, your prescription is dispensed by post. Costs range from £129–£320 per month depending on dose and provider. Both routes require a proper clinical assessment. Our GLP-1 weight loss calculator can help you estimate projected outcomes at different doses, supporting discussions with your prescriber about realistic expectations.
- 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.
What exactly comes in a Mounjaro starter bundle?
A Mounjaro starter bundle is typically one Mounjaro KwikPen pre-filled with 2.5 mg tirzepatide (enough for 4 weekly injections). It includes the pen, 4 needles, and instructions. Some suppliers may bundle additional guidance materials. Always check what your provider includes.
Can I skip the starter dose and go straight to 5 mg?
No. MHRA guidance and clinical practice in the UK require starting at 2.5 mg for 4 weeks minimum, regardless of target dose. This reduces side effects and allows your body to adjust. Skipping steps increases nausea and other adverse reactions.
How long does a Mounjaro starter pack last?
One KwikPen with the 2.5 mg dose contains exactly 4 weekly injections, lasting 4 weeks. After that, your prescriber will either maintain you at 2.5 mg or escalate you to 5 mg based on your response.
Am I eligible for Mounjaro on the NHS with a BMI of 28?
If your BMI is 28 and you have a weight-related health condition (diabetes, high blood pressure, etc.), you may be eligible. For South Asian, Chinese, Black African, or Black Caribbean heritage, eligibility starts at BMI 27.5. Ask your GP to refer you to your local NHS tier 3 weight management service for assessment.
What's the difference between Mounjaro vs Wegovy for NHS prescribing?
Both are available via NHS specialist services under NICE guidance. Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist starting at 2.5 mg; Wegovy (semaglutide) is a GLP-1 agonist starting at 0.25 mg. Both show similar average weight loss (~15–21%), though individual results vary. Your prescriber will choose based on clinical suitability.
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.