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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Bleeding on Mounjaro — What You Need to Know
Bleeding is not listed as a common side effect of Mounjaro (tirzepatide) in UK clinical trials or product information. However, if you experience any unusual bleeding — including nosebleeds, bleeding gums, bruising more easily than normal, or blood in urine or stools — you should contact your GP or seek urgent medical attention. This guide explains what bleeding symptoms mean, when to get help, and how Mounjaro may indirectly affect bleeding risk through other health mechanisms.
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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.
Is Bleeding a Direct Side Effect of Mounjaro?
Bleeding is not listed as a common or uncommon side effect in the Mounjaro prescribing information or SURMOUNT clinical trials that led to UK approval. However, bruising and injection site reactions are common — approximately 1 in 10 users may experience redness, bruising, or mild discomfort at the injection site where the Mounjaro KwikPen is used.
What matters is distinguishing between:
- Normal injection site bruising — minor discolouration that fades within days
- Unusual bleeding — bleeding from the nose, gums, urine, stools, or unexplained bruising appearing spontaneously across the body
If you notice unusual bleeding unrelated to your injection site, this is not a known Mounjaro effect and warrants immediate medical assessment. Seek urgent medical advice if bleeding is severe or persistent.
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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.
When to Contact Your GP About Bleeding
Contact your GP or NHS 111 if you experience:
- Spontaneous nosebleeds without injury
- Blood in urine (pink or red-tinged urine)
- Blood in stools (black stools or visible red blood)
- Unexplained bruising or bruising that appears easily after minor bumps
- Bleeding from the gums or bleeding when brushing teeth
- Any other unusual bleeding
Seek emergency care (call 999 or attend A&E) if bleeding is heavy, does not stop within 10 minutes, or you feel unwell. While these symptoms are not known Mounjaro side effects, they may indicate an underlying health condition that requires prompt assessment, particularly if you have recently started tirzepatide.
- 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.
Can Mounjaro cause bleeding?
Bleeding is not listed as a known side effect of Mounjaro in UK clinical trials or product information. Minor bruising at injection sites is common, but unusual bleeding from other parts of the body is not a recognised Mounjaro effect. If you experience unexplained bleeding, contact your GP — it may indicate another health issue unrelated to the medication.
Is bleeding more likely if I take Mounjaro and other medications?
Mounjaro itself does not increase bleeding risk, but if you take blood-thinning medications (such as warfarin or aspirin), any new medication can interact. Always inform your prescriber of all medications you take. They will assess whether any interactions could affect bleeding risk or medication absorption.
What should I do if I get a bad bruise from my Mounjaro injection?
Minor bruising at the injection site is normal and usually fades within days. Apply gentle pressure if bleeding occurs during injection. Rotate injection sites weekly (stomach, thigh, upper arm) to avoid repeated bruising in the same area. If bruising is severe, very painful, or accompanied by swelling, contact your GP.
Could Mounjaro affect my bleeding risk indirectly?
Mounjaro works by regulating appetite and blood sugar through GIP and GLP-1 pathways — it does not directly affect blood clotting. However, if you have type 2 diabetes or cardiovascular disease, Mounjaro may improve these conditions, which could theoretically reduce bleeding complications. Your GP can assess your individual bleeding risk.
Should I stop Mounjaro if I notice bleeding?
Do not stop Mounjaro without advice from your prescriber. If you experience unusual bleeding, contact your GP or NHS 111 to discuss what you've noticed. Your prescriber will assess whether the bleeding is related to Mounjaro, another medication, or a separate health issue, and advise whether to continue or pause your prescription.
Ready to take control of your weight loss journey?
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