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 Pen Stuck on Last Dose — What You Need to Know
If your Mounjaro KwikPen is stuck on the last dose, don't worry — this is a common question among people using this tirzepatide injection. Whether you're on the NHS waiting list or considering private prescription access, understanding your options for continuing treatment is essential. This guide explains UK costs, how to access Mounjaro through both NHS and private routes, and what happens when you need your next pen.
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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.
Understanding Mounjaro Access and Cost in the UK
Mounjaro (tirzepatide) is available through two main routes in the UK: NHS specialist weight management services and private prescription through licensed online providers. Each path has different costs and timelines.
- NHS route: Free at the point of use through specialist tier 3 weight management services, but access varies significantly by region and waiting lists can extend many months
- Private route: Costs typically range from £129–£320 per month depending on dose. Each KwikPen contains 4 weeks' supply (4 doses)
- Prescription requirement: Whether NHS or private, Mounjaro is prescription-only and requires a clinical assessment confirming your eligibility based on BMI and weight-related health conditions
- Dose progression: Treatment follows a dose titration schedule — you'll typically start at 2.5 mg and increase weekly up to your effective maintenance dose (often 10 mg or 15 mg)
When your current pen runs out, you'll need to arrange your next supply through your existing provider — either request a repeat prescription from NHS services or place a repeat order through private prescribing if that's your route.
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: Eligibility, Timeline, and Next Steps
NHS route: Ask your GP for referral to your local tier 3 weight management service. You must have a BMI of 30 or above (or 27+ with weight-related conditions like type 2 diabetes, hypertension, or sleep apnoea). Waiting times vary — some areas have 12+ month waits. NICE has approved tirzepatide for NHS use, but regional availability remains inconsistent.
Private route: Complete an online consultation with a UK-licensed prescriber (takes 10–20 minutes). If approved, your prescription is sent to a GPhC-registered pharmacy who'll dispense and post your pen. Most people receive their first order within 5–7 working days. Use our GLP-1 weight loss calculator to estimate potential results while awaiting your next supply.
Continuity: Neither route has a "break" in treatment — simply arrange your next pen before your current supply runs out.
- 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's the cost of Mounjaro on private prescription in the UK?
Private Mounjaro typically costs £129–£320 per month depending on your dose. Each KwikPen provides 4 weekly injections (one month's supply). Prices vary between providers. You'll pay per dose increase during titration, then continue at your maintenance dose.
Can I get Mounjaro free on the NHS?
Yes, if you're referred to an NHS specialist weight management service and meet eligibility criteria (BMI ≥30, or ≥27 with weight-related conditions). However, regional availability is very limited and waiting lists can be 12+ months in many areas.
What if my Mounjaro pen feels stuck — is it broken?
KwikPens sometimes feel resistant when nearing the final dose. Check the dose counter window — if it shows 0.00 or the pen is empty, it's functioning normally and simply exhausted. Order your next pen. If the pen feels stuck before the final dose, contact your provider for guidance.
How long does it take to get Mounjaro through private prescription?
Most private providers complete your online consultation within hours. If approved, your prescription is issued and sent to a pharmacy. You'll typically receive your first pen within 5–7 working days by post.
Do I need a GP referral to get Mounjaro privately?
No. Private Mounjaro requires only an online clinical assessment with a UK-licensed prescriber — no NHS referral needed. However, it's good practice to inform your GP you're using weight loss medication so they can monitor your progress.
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.