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 Injection Site Reactions — UK Access & Cost
Injection site reactions are common with Mounjaro and typically mild. This guide explains what injection site reactions are, how to manage them, and how to access Mounjaro in the UK — whether through NHS specialist services or private prescription following a clinical assessment. Understanding both the side effect profile and your access options helps you make an informed decision about this weekly weight loss injection.
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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.
What Are Mounjaro Injection Site Reactions?
Injection site reactions are local reactions at the area where you inject Mounjaro. They are classified as common side effects, affecting up to 1 in 10 people using this weekly weight loss injection. Typical reactions include redness, bruising, pain, swelling, or itching at the injection site. These reactions usually appear shortly after injection and typically resolve within a few hours or days without treatment.
- Redness or inflammation around the injection point
- Bruising or discolouration of the skin
- Mild to moderate pain or tenderness
- Swelling or puffiness at the site
- Itching or a burning sensation
Most injection site reactions are mild and temporary, and do not require you to stop using Mounjaro. However, rotating your injection sites each week (stomach, upper thigh, or upper arm) can help minimise the risk. If you experience severe reactions — such as excessive swelling, signs of infection, or persistent problems — contact your GP or the healthcare professional managing your Mounjaro treatment.
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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.
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Accessing Mounjaro in the UK — NHS vs Private Cost
In the UK, Mounjaro is available through two routes. NHS access is through specialist tier 3 weight management services following referral from your GP, though waiting lists vary significantly by region. Private access is available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. Private costs typically range from £129 to £280+ monthly depending on your maintenance dose, with starting doses costing less than higher doses. Both routes require a clinical assessment to confirm suitability — you cannot obtain Mounjaro without a valid prescription and clinical evaluation.
- NHS: Free on prescription once prescribed by a specialist service (no direct patient cost)
- Private: £129–£280+ per month depending on dose level and provider
- Both routes require prescription and clinical assessment
For NHS access: Ask your GP about referral to your local tier 3 weight management service. Eligibility typically requires BMI of 30 or above, or 27–29.9 with weight-related health conditions. NHS waiting times can be several months or longer depending on your region. For private access: Online consultations involve completing a health questionnaire and having a video or telephone assessment with a registered prescriber. If approved, your prescription is dispensed by a pharmacy and posted to your address. The entire process typically takes 2–5 working days. Try our GLP-1 weight loss calculator to explore potential outcomes at different Mounjaro doses, and use our BMI calculator to check your eligibility based on current guidelines.
- 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 exactly is an injection site reaction with Mounjaro?
An injection site reaction is a local response at the area where you inject Mounjaro. Common symptoms include redness, bruising, mild pain, swelling, or itching. These usually appear shortly after injection and resolve within hours or days. They are classified as a common side effect affecting up to 1 in 10 users. Most are mild and do not require stopping treatment.
How can I reduce injection site reactions when using Mounjaro?
Rotate your injection site each week between your stomach, upper thigh, and upper arm. Let your skin fully dry after cleaning if you clean the injection area. Use a new needle for each injection and ensure you are injecting correctly — your prescriber should demonstrate proper technique. Most reactions decrease over time as your body adjusts.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs typically range from £129 to £280+ per month depending on your dose. Starting doses (2.5 mg) are usually at the lower end, whilst higher maintenance doses (15 mg) cost more. Prices vary slightly between private prescribing providers. NHS prescription is free once prescribed by a specialist service, but access requires referral and assessment.
Is Mounjaro available on the NHS in the UK?
Yes, Mounjaro is available on the NHS through specialist tier 3 weight management services. You need a referral from your GP and must meet eligibility criteria (BMI 30+ or 27–29.9 with weight-related conditions). However, NHS access varies by region and waiting lists can be lengthy. Private prescription is an alternative route if NHS waiting times are prohibitively long.
What's the difference between Mounjaro and Wegovy for injection site reactions?
Both are prescription-only weekly weight loss injections and both can cause injection site reactions as a common side effect. Mounjaro is a dual GIP/GLP-1 agonist, whilst Wegovy is a GLP-1 agonist only. Clinical trial data shows similar frequencies of injection site reactions between the two. Your prescriber will assess which is most appropriate based on your individual health profile and eligibility.
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