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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Side Effects of 5mg Mounjaro — Cost and Access in the UK
The 5mg dose is Mounjaro's first maintenance dose, typically reached after four weeks of treatment. At this stage, side effects are often mild but can still occur. This guide explains what you might experience on 5mg, how to access tirzepatide in the UK, and the cost differences between NHS and private routes. Understanding both the effects and the access options helps you make an informed decision about whether this prescription-only medication is right for you.
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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.
Common Side Effects at 5mg and Private Prescription Costs
The 5mg dose is the first maintenance level of Mounjaro, reached in week 5 of treatment. At this dose, nausea remains the most frequently reported side effect, affecting approximately 20–30% of users, though it typically improves after a few weeks as your body adjusts. Other common effects include diarrhoea, constipation, and mild stomach discomfort. Many users experience reduced appetite, which is the intended therapeutic effect.
In the UK, accessing 5mg Mounjaro privately through a UK-licensed prescriber costs between £129 and £200 per month, depending on the provider and prescription service. This covers the KwikPen (which contains four weekly doses) plus the online clinical assessment. This is significantly cheaper than higher doses like 10mg or 15mg, which typically cost £200–£280 monthly. Costs vary because different online prescription services set their own fees. NHS access, by contrast, is free at the point of use but requires referral to a specialist tier 3 weight management service and often involves substantial waiting times across most regions.
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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 Access — Which Route Suits You?
Accessing Mounjaro through the NHS involves being referred by your GP to a specialist weight management service (tier 3). NICE has approved tirzepatide for NHS use, but availability varies significantly by region, and waiting lists can exceed six months in many areas. If you qualify clinically and gain NHS access, the medication is free, making it the most cost-effective long-term option.
The private route offers faster access. An online consultation with a UK-licensed prescriber (usually takes 24–48 hours) determines your eligibility. If approved, your prescription is dispensed by a GPhC-registered pharmacy. This route suits people who want to start treatment quickly or live in areas with limited NHS specialist services. Both routes require a clinical assessment to confirm your BMI and health status. Use our free GLP-1 weight loss calculator to understand potential outcomes at 5mg before committing to treatment.
- 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 5mg Mounjaro available on the NHS in the UK?
Yes, Mounjaro is NICE-approved for NHS use through specialist weight management services. However, access requires GP referral to tier 3 services and varies by region. Waiting times can be several months. If you qualify and gain NHS access, the medication is free.
How much does 5mg Mounjaro cost privately in the UK?
Private prescription costs for 5mg Mounjaro typically range from £129–£200 per month through UK online prescribing services. This includes the KwikPen and clinical assessment. Costs vary between providers, so comparing options before committing is advisable.
What is the difference between 5mg and higher doses like 10mg?
5mg is the first maintenance dose (started week 5). Higher doses like 10mg or 15mg typically have stronger appetite-suppressing effects and greater weight loss potential, but they cost more (£200–£280 monthly) and may increase side effect likelihood.
How long does an online prescription assessment take for 5mg Mounjaro?
Most UK online clinical assessments take 24–48 hours. You'll answer health questions, and a UK-licensed prescriber reviews your answers. If approved, your prescription is sent to a pharmacy and dispatched within 1–2 working days.
Can I switch between NHS and private Mounjaro prescriptions?
Switching between NHS and private prescriptions requires coordination with your healthcare provider. If you start private treatment, inform your GP. If you later gain NHS access, your prescriber can facilitate a handover to avoid interruption to treatment.
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.