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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What to Expect on Mounjaro Day 4 — Cost and Access in the UK
Day 4 is still within your first week of Mounjaro treatment — you're just days into your starting dose of 2.5 mg. Understanding the full cost and access picture for tirzepatide in the UK helps you plan your treatment journey. Whether you're considering private prescription access or exploring NHS specialist services, knowing UK pricing, eligibility criteria, and how the dose titration process works ensures you can make an informed decision about this GLP-1 receptor agonist with your 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.
Mounjaro Cost and Access in the UK
Private prescription costs: Mounjaro through private online consultation services typically costs between £129 and £320 per month depending on your dose. The starting dose (2.5 mg) is usually at the lower end of this range, whilst higher doses like 15 mg cost more. Each KwikPen contains 4 weeks' supply of once-weekly injections. Private access doesn't require NHS referral — you complete an online clinical assessment with a UK-licensed prescriber, and if suitable, a prescription is issued and dispensed by a GPhC-registered pharmacy.
NHS access: Through specialist tier 3 weight management services, tirzepatide may be available free at point of care — but NHS access is limited by regional availability and waiting lists can be substantial in many areas. Your GP can refer you to your local specialist service if you meet NICE eligibility criteria (BMI 30+ or 27+ with weight-related conditions). NHS access typically requires documented attempts at lifestyle intervention first.
Dose titration costs: Starting at 2.5 mg, your dose increases every 4 weeks if tolerated. This means ongoing costs increase as you progress through the dose escalation schedule over several months.
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 Routes — How to Access Mounjaro
NHS route: Referral from your GP to a tier 3 specialist weight management service. You'll be assessed for eligibility and safety before starting. Waiting times vary by region (ICB) but can range from weeks to many months in some areas. Once approved, Mounjaro is dispensed free through the NHS. This is the recommended first-line route if available in your area.
Private route: Book an online consultation with a UK-licensed prescriber (no GP referral needed). Provide medical history via an online form. If approved, a prescription is sent to a GPhC-registered pharmacy for dispensing. This typically takes 2–5 working days. Use our GLP-1 weight loss calculator to estimate potential outcomes at different doses, and consult your prescriber about cost vs expected results.
Online consultation process: Private consultations are conducted via secure online platforms. You'll answer questions about your medical history, current medications, weight, height, and health goals. The prescriber assesses whether tirzepatide is suitable and safe for you. If approved, a prescription is issued valid at any GPhC-registered UK pharmacy. Prescriptions cost separately from the medication itself (typically £15–30). Always ensure your prescriber asks about oral contraceptives (if applicable) — Mounjaro may reduce their effectiveness.
- 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.
Is Mounjaro available on the NHS in the UK?
Yes, tirzepatide (Mounjaro) is available through NHS specialist weight management services for adults with a BMI of 30 or above, or 27+ with weight-related health conditions. However, availability is limited by region and waiting lists can be very long. Your GP can refer you to your local tier 3 service to check eligibility and current waiting times.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs range from approximately £129–£320 per month depending on your dose. The starting 2.5 mg dose is typically cheaper than higher doses. Each KwikPen (4-week supply) costs separately. Prescriber fees (typically £15–30) are additional. Always ask for transparent pricing before starting.
What dose will I be on day 4 of Mounjaro?
On day 4, you'll still be on your starting dose of 2.5 mg — this is your first and only injection of week 1. Your dose remains at 2.5 mg for a full 4 weeks (weeks 1–4) before increasing to 5 mg in week 5. This slow titration minimises side effects as your body adjusts.
Can I switch from private to NHS Mounjaro?
In theory, yes — you could request NHS referral whilst on private treatment. However, NHS services may require you to restart the dose titration from 2.5 mg rather than continuing your current dose. It's best to discuss this with your GP or NHS specialist service directly, as protocols vary by region.
What's included in the Mounjaro KwikPen cost?
Each pre-filled KwikPen contains 4 once-weekly injections (4 weeks' supply). The cost covers the medication only — you still need to pay a separate prescription fee to the pharmacy. Storage is in a refrigerator (2–8°C unopened, up to 30 days at room temperature after first use). Always store safely away from children and pets.
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.