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, Calorie Deficit, and Weight Loss — UK Access Guide
Mounjaro (tirzepatide) is a prescription-only injection that works alongside a reduced-calorie diet to support weight loss. Understanding how it fits into a calorie deficit strategy — and how to access it in the UK — helps you decide if it's right for you. This guide covers NHS and private routes, typical costs, and what the prescription process involves. Use our free GLP-1 weight loss calculator to estimate potential results at different Mounjaro doses alongside dietary changes.
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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 Private Access in the UK
Private prescription costs for Mounjaro in the UK typically range from £129 to £320 per month, depending on the dose and provider. Starting doses (2.5 mg) are usually cheaper; maximum doses (15 mg) cost more. Many people access Mounjaro privately through GPhC-registered online prescribing services without waiting for NHS referrals. The private route involves an online clinical assessment with a UK-licensed prescriber, who decides if Mounjaro is suitable based on your BMI, health history, and any weight-related conditions. If approved, a prescription is issued and dispensed by a registered pharmacy. Private access is straightforward but not covered by NHS funding. Each KwikPen contains four weekly doses and costs reflect the dose strength — higher doses mean higher monthly costs.
- Starting dose (2.5 mg): approximately £129–£160/month
- Mid-range doses (5–10 mg): approximately £180–£240/month
- Maximum dose (15 mg): approximately £280–£320/month
Individual pricing varies by provider. Always confirm costs upfront before starting treatment.
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 Access vs Private Route — What to Expect
NHS access to Mounjaro is through tier 3 specialist weight management services following a GP referral. NICE has approved tirzepatide for NHS use, but availability depends on your region (ICB). NHS waiting lists can be very long — months to years in some areas. Once assessed, NHS treatment is free, but you must meet strict eligibility criteria and attend specialist appointments. Private access is faster: apply online, have a clinical assessment (usually within days), receive a prescription, and start treatment. There's no referral needed. Both routes require a clinical assessment confirming your BMI and health status. Use our BMI calculator to check your current BMI and see if you meet eligibility thresholds (BMI 30+, or 27+ with weight-related conditions like diabetes or high blood pressure).
- 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 difference between NHS and private Mounjaro access in the UK?
NHS access requires a GP referral to specialist services, is free but has long waiting lists (often months or years). Private access is faster (days to weeks), costs £129–£320/month depending on dose, requires an online clinical assessment, and needs no NHS referral. Both require you to meet eligibility criteria.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs range from approximately £129/month for starting doses (2.5 mg) to £320/month for maximum doses (15 mg). Costs depend on the specific dose prescribed and your provider. Always confirm pricing with the prescribing service before starting treatment.
How does Mounjaro work with a calorie deficit?
Mounjaro (tirzepatide) is a GIP and GLP-1 receptor agonist that may help reduce appetite and support feeling fuller after smaller meals. It works best alongside a reduced-calorie diet and increased activity — the medication supports the calorie deficit, not replacing it. Clinical trials showed average weight loss of 15–21% alongside dietary changes.
What's the online prescription process for Mounjaro in the UK?
You complete an online health questionnaire, have a consultation with a UK-licensed prescriber (often via video or phone), and if approved, receive a prescription. A GPhC-registered pharmacy dispenses the medication, usually within days. The whole process typically takes 1–2 weeks from application to receiving your first KwikPen.
Am I eligible for Mounjaro on the NHS in the UK?
NHS eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related conditions (diabetes, high blood pressure, sleep apnoea). South Asian, Chinese, Black African, and Caribbean adults may qualify at slightly lower BMIs. Your GP or specialist will assess your individual situation. Use our free BMI calculator to check your current BMI.
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.