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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Does Mounjaro Cause Bruising? What You Need to Know
Bruising and injection site reactions are common with Mounjaro, but they're usually mild and temporary. This guide explains why bruising happens, what to expect, how much Mounjaro costs in the UK through private prescription, and the different routes to access this tirzepatide injection safely. Whether you're considering Mounjaro through the NHS or privately, understanding the full picture — including injection site effects and costs — helps you make an informed decision.
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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.
Does Mounjaro Cause Bruising and Injection Site Reactions?
Yes, bruising and injection site reactions are among the most common side effects of Mounjaro (tirzepatide). According to UK clinical guidance and the product information, injection site reactions occur in up to 1 in 10 people taking Mounjaro. These typically include redness, bruising, swelling, pain, or itching at the injection site.
Bruising after a Mounjaro injection is usually mild and self-limiting — meaning it resolves on its own within a few days to a week without treatment. The KwikPen needle is very fine (29 gauge), which minimises tissue trauma, but individual factors like bleeding tendency, skin sensitivity, and injection technique affect bruising severity.
- Most bruising fades within 3–7 days
- Applying ice immediately after injection may reduce bruising
- Rotating injection sites weekly helps prevent accumulation
- Bruising does not mean the injection failed or the dose is wrong
- Severe or persistent injection site reactions should be reported to your prescriber
If you experience unusual bruising, swelling that doesn't improve, or signs of infection (warmth, increasing pain, discharge), contact your GP or prescriber.
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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 in the UK: Private Prescription Pricing and NHS Access Routes
Private prescription costs for Mounjaro vary by dose and provider, typically ranging from £150–£320 per month depending on which dose you're prescribed. Starting doses (2.5 mg) are usually at the lower end, whilst maintenance or higher doses (10 mg–15 mg) cost more. Prices include the clinical assessment, prescription, and delivery.
NHS access through specialist weight management services is free once referred, but availability varies significantly by region and waiting lists can be lengthy. To access Mounjaro via the NHS, you'll need referral to a tier 3 weight management service from your GP. NICE has approved tirzepatide, but regional ICBs control actual provision. Many people choose private prescription to avoid NHS waiting times — an online consultation with a UK-licensed prescriber can take place within days, with medication delivered within a week.
Check your personal BMI using our free BMI calculator to understand your eligibility before seeking a prescription. Both routes require clinical assessment to confirm you meet eligibility criteria (BMI 30 or above, or 27–29.9 with weight-related health conditions).
- 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 long does Mounjaro bruising last?
Most bruising from a Mounjaro injection fades within 3–7 days. If bruising persists beyond two weeks or worsens, contact your GP or prescriber. Applying ice immediately after injection and rotating injection sites each week can reduce bruising severity.
Can I prevent bruising when using the Mounjaro KwikPen?
While bruising cannot always be prevented, you can reduce risk by rotating injection sites weekly (stomach, thigh, or upper arm), allowing the skin to warm before injecting, using proper injection technique, and applying gentle pressure for 5–10 seconds after. Ask your prescriber or pharmacist for injection technique guidance.
How much does Mounjaro cost on private prescription in the UK?
Private prescription costs range from approximately £150–£320 per month depending on your prescribed dose. Starting doses (2.5 mg) are usually cheaper; higher maintenance doses (10–15 mg) cost more. Prices include the clinical assessment, prescription, and delivery to your home.
How do I get Mounjaro prescribed in the UK — NHS or private?
NHS: referral from your GP to a specialist tier 3 weight management service (free but long waiting lists). Private: online consultation with a UK-licensed prescriber (usually within days), prescription issued if clinically appropriate, then dispensed by a registered pharmacy. Both routes require a clinical assessment.
Is Mounjaro the same as Wegovy, and do they have similar injection site effects?
No — Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist, whilst Wegovy (semaglutide) is a GLP-1 agonist only. Both can cause injection site reactions including bruising. Clinical trials show similar rates of mild injection site reactions for both medications. Your prescriber can advise which is more suitable for you.
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