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 Bruise — UK Cost and Access Guide
Bruising at the injection site is a common side effect when starting Mounjaro (tirzepatide), the weekly weight loss injection licensed in the UK. This guide explains why bruising occurs, what you can do about it, and how to access Mounjaro through both NHS and private routes. Understanding both the practical side effects and the cost of accessing this prescription medication helps you make an informed decision about weight management options available to you. Use our free BMI calculator and GLP-1 weight loss calculator to explore whether this treatment might be suitable for your situation.
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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.
What Causes Mounjaro Injection Bruising?
Injection site bruising is a common side effect when starting Mounjaro, particularly during the first few weeks as your body adjusts. Bruising occurs because the needle penetrates small blood vessels under the skin, causing minor bleeding into surrounding tissues. This is a normal physiological response and typically indicates no serious problem.
Factors that increase bruising risk include:
- Using a new injection site each week (rotation is required, which can increase bruising frequency initially)
- Injecting into areas with more fatty tissue or visible blood vessels
- Taking blood-thinning medications (aspirin, warfarin)
- Certain health conditions affecting blood clotting
- Injecting too quickly or at an incorrect angle
- Pressing on the site immediately after injection
Most injection site bruises resolve within 1–2 weeks and fade naturally. They are not a reason to stop Mounjaro unless they are severe or accompanied by swelling, warmth, or redness suggesting infection.
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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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Mounjaro Cost and Access — NHS vs Private in the UK
Accessing Mounjaro in the UK depends on whether you pursue NHS or private routes, which differ significantly in cost and waiting times.
NHS Access: Mounjaro is NICE-approved for use within NHS specialist weight management services. Access is through tier 3 specialist services, typically requiring GP referral. However, NHS availability varies substantially by region and waiting lists can extend several months or longer. When available on the NHS, treatment is free at point of use.
Private Access: Available through GPhC-registered online prescribing services following an online clinical assessment. Costs typically range from £129–£320 per month depending on your dose. Mounjaro KwikPen devices cost more at higher doses (15mg is the maximum dose). Private prescriptions are dispensed by registered pharmacies and can be obtained without NHS referral, offering faster access than NHS routes. Online consultations usually take 24–48 hours for assessment and prescription.
- 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.
Why do Mounjaro injections cause bruising?
Bruising occurs when the needle penetrates small blood vessels under the skin during injection, causing minor bleeding into surrounding tissues. This is a normal response and not dangerous. Bruising is more common when rotating injection sites weekly, as you're using different areas of skin. Most bruises fade within 1–2 weeks naturally.
Can I prevent bruising when using my Mounjaro KwikPen?
Yes, several steps reduce bruising: inject at room temperature (not cold), allow the injection site to warm slightly, pinch the skin gently, inject slowly, avoid pressing the site immediately after injection, and do not massage the area. Choosing injection sites with thinner skin (upper arm, thigh) rather than the stomach may also help, though rotation is still required.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs typically range from £129–£320 per month depending on your dose. Starting doses (2.5mg–5mg) are cheaper; maximum dose (15mg) is more expensive. Costs vary slightly between online prescribing services. Most offer monthly subscriptions or per-dose pricing. Always check the specific cost before starting treatment.
Can I get Mounjaro on the NHS in the UK?
Yes, Mounjaro (tirzepatide) is NICE-approved for NHS specialist weight management services. Access requires GP referral to your local tier 3 specialist service. Availability and waiting times vary significantly by region. Treatment is free when available on the NHS, but delays can be substantial. Private access is faster if you're willing to pay.
What should I do if my Mounjaro injection bruises are severe?
Most injection site bruises are mild and resolve within 1–2 weeks. Seek medical advice if bruising is accompanied by severe swelling, warmth, redness, or pus (signs of infection), or if bruises are unusually large or painful. Your GP or prescriber can advise whether to continue treatment or adjust your injection technique. Ice packs can help reduce bruising after injection.
Ready to take control of your weight loss journey?
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