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 First Month Weight Loss — What to Expect in the UK
During your first month on Mounjaro, weight loss results vary significantly between individuals — some people notice changes within the first few weeks, while others see minimal weight loss initially. Your first dose is typically a 2.5 mg starting injection, which your body needs time to adjust to. Understanding what to realistically expect, how much Mounjaro costs in the UK, and the different ways to access this prescription weight loss injection can help you make an informed decision about whether it's right for you. This guide covers the cost, access routes, and the medical assessment process.
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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 in the UK and Private Access Routes
Mounjaro is available in the UK through two main routes: NHS specialist weight management services and private prescription through GPhC-registered online pharmacies. Private prescription costs typically range from £129 to £199 per month for a starter dose (2.5–5 mg), increasing to £179–£249 for higher maintenance doses (10–15 mg). These prices vary between providers and may include the online consultation fee. Each KwikPen contains 4 weekly injections — one month's supply — so costs are monthly. NHS access is free if eligible, but availability varies dramatically by region and waiting lists can be lengthy. A private consultation with a UK-licensed prescriber usually costs £30–£50 and takes 10–15 minutes, covering your medical history, BMI, weight-related health conditions, and current medications to assess whether Mounjaro is suitable for you.
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: How to Access Mounjaro in Your First Month
NHS route: Ask your GP for a referral to your local tier 3 specialist weight management service. You'll be assessed and may be prescribed Mounjaro free of charge, but regional ICB funding varies and waiting lists can extend several months. Private route: Complete an online consultation with a UK-licensed prescriber through a private pharmacy. If approved, your prescription is sent directly to a GPhC-registered pharmacy, and Mounjaro is dispatched to you. The private route is typically faster — often within 3–7 days. Both routes require a clinical assessment; no one can prescribe Mounjaro without reviewing your health status. Your GP should always be informed if you're taking Mounjaro, even if prescribed privately, to monitor your progress and check for interactions with other medications.
- 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.
How much weight will I lose in my first month of Mounjaro?
Individual results vary significantly. Clinical trials showed average weight loss of around 3–5 kg in the first month, but some people lose less initially while their body adjusts to the 2.5 mg starting dose. Weight loss typically increases as your dose is gradually increased over subsequent weeks. Use our GLP-1 weight loss calculator to see projected results at different doses, though your actual outcome will depend on your diet, activity, genetics, and metabolism.
Is Mounjaro available on the NHS for weight loss in the UK?
Yes, Mounjaro has been approved by NICE for NHS use in specialist tier 3 weight management services. However, availability varies by region and waiting times can be months. Eligibility typically requires a BMI of 30 or above, or 27+ with weight-related health conditions. Contact your GP for a referral to your local specialist service to check availability in your area.
How quickly can I get Mounjaro through private prescription?
The private route is usually faster than NHS referral. After completing an online consultation (10–15 minutes), if approved, your prescription can be dispensed within 3–7 days by a GPhC-registered pharmacy. Costs range from £129–£199 per month for starter doses. This is faster than NHS routes but requires private payment.
What happens during the first month if I experience side effects?
Common first-month side effects include nausea, diarrhoea, and reduced appetite — these often improve within a few weeks. Contact your prescriber (NHS or private) immediately if you experience severe stomach pain, persistent vomiting, or signs of allergic reaction. Never stop Mounjaro without speaking to your prescriber, as they may adjust your dose or provide additional support.
Will my GP need to know if I get Mounjaro privately?
Yes — inform your GP that you're taking Mounjaro, even if prescribed privately. Your GP can monitor your progress, check for drug interactions with other medications you take, and provide holistic support for your weight loss journey. NHS and private care work best together.
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.