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
How Much Is 15 Mg Mounjaro in the UK?
The maximum dose of Mounjaro (tirzepatide) is 15 mg once weekly, but the cost varies significantly depending on whether you access it through the NHS or privately. On the NHS, tirzepatide is available through specialist weight management services at no direct cost to you (covered by your prescription charges, typically £9.90 per item in England). Privately, 15 mg Mounjaro costs between £200 and £280 per month depending on your prescriber and pharmacy. Most people don't start at 15 mg — the dose is gradually increased from 2.5 mg over several weeks, so initial costs are lower.
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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.
Private Prescription Costs for 15 Mg Mounjaro in the UK
When accessing Mounjaro privately, a 15 mg KwikPen (containing 4 weekly doses) typically costs £200–£280 per month through UK-regulated online pharmacies. This price includes the prescription fee (usually £15–£25) assessed by a UK-licensed prescriber during an online consultation. The exact cost depends on which registered pharmacy you use — prices do vary, so it's worth comparing.
Most patients don't pay for 15 mg from the start. The standard dose titration schedule means you begin at 2.5 mg (weeks 1–4), then increase gradually: 5 mg (weeks 5–8), 7.5 mg (weeks 9–12), 10 mg (weeks 13–16), 12.5 mg (weeks 17–20), and finally 15 mg (week 21 onwards). This means your first month costs significantly less than the full 15 mg price. Many people reach their target weight loss at lower doses (5 mg or 10 mg), so full-price 15 mg treatment isn't always necessary.
- Private online consultation: £15–£25
- 15 mg Mounjaro per month: £200–£280
- Total first month (lower dose): typically £50–£100
- Subsequent months: higher as dose increases
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: Which Route Is Right for You?
NHS route: Completely free if prescribed through a tier 3 or 4 specialist weight management service. However, access is competitive — you must be referred by your GP, and waiting lists can be 6–18 months depending on your area. Not all NHS services currently offer tirzepatide; availability varies by Integrated Care Board (ICB). NICE has approved Mounjaro for NHS use, but regional funding decisions mean your local service may prioritise semaglutide (Wegovy) or liraglutide (Saxenda) instead.
Private route: Faster access (usually within days), no referral needed, and you control which medication you use. You pay per dose, but you start treatment immediately and can stop at any time. The online consultation process takes 15–30 minutes, and your prescription is issued the same day if approved. This route suits people who cannot wait for NHS services or prefer assured access.
Use our free GLP-1 weight loss calculator to estimate potential results at different doses, then discuss your best access route with your GP or a licensed prescriber.
- 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 15 mg Mounjaro the dose everyone needs?
No. Clinical trials showed that average weight loss at 15 mg was approximately 20.9% of body weight, but many people achieve meaningful weight loss at lower doses (5 mg, 10 mg, or 12.5 mg). Your prescriber will assess the right dose for you based on your health, goals, and response to treatment. The dose titration schedule means you start low and increase gradually — most people find their optimal dose before reaching 15 mg.
Can I get 15 mg Mounjaro 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 health conditions). However, availability varies by region, and waiting lists can be very long. Your GP can check whether your local ICB funds tirzepatide specifically — some areas may offer other GLP-1 medications instead. Ask your GP about your local tier 3 weight management service.
How long does a 15 mg Mounjaro KwikPen last?
One KwikPen contains 4 weekly doses of 15 mg, so it lasts 4 weeks (one month). You inject once per week on the same day each week. Each KwikPen comes as a pre-filled pen that you use at home — no preparation needed. Store unopened pens in the fridge at 2–8°C; after first use, it can stay at room temperature for up to 30 days.
Why does private Mounjaro cost more than some other weight loss injections?
Prices vary between different GLP-1 and GIP/GLP-1 medications and between different providers. Tirzepatide (Mounjaro) is newer and involves a dual mechanism (GIP + GLP-1), which some private services price slightly higher than single-mechanism GLP-1 injections like semaglutide. However, prices are competitive — always check with multiple registered UK pharmacies to compare. Your prescriber can discuss which medication offers the best value for your situation.
What happens if I can't afford 15 mg treatment privately?
Several options: you could start at a lower dose (5 mg or 10 mg costs less monthly), pause treatment temporarily, or apply to your GP for NHS referral to specialist services. Some private prescribing services offer flexible payment plans. If cost is a barrier, discuss this openly with your prescriber — they may suggest starting lower or exploring timing options. Weight loss is a long-term journey; affordability matters.
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.