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
Free tracker included with every download this week
Can You Take Mounjaro With Blood Thinners?
If you're taking blood thinning medication and considering Mounjaro (tirzepatide) for weight management, it's important to understand how these medicines may interact. Mounjaro is a prescription-only GLP-1 and GIP receptor agonist injection licensed in the UK for weight management in eligible adults. There is no direct interaction between tirzepatide and blood thinners, but your prescriber needs to know about all medications you're taking before starting treatment. Your GP or licensed prescriber will assess your individual circumstances to ensure Mounjaro is safe for you.
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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 You Need to Tell Your Prescriber
Before starting Mounjaro, you must inform your prescriber about every medication you take, including any blood thinners such as warfarin, apixaban, rivaroxaban, dabigatran, edoxaban, aspirin, or others. This is essential because:
- Your prescriber needs a complete picture of your health to assess safety
- Some medications can affect how others work in your body
- Weight loss itself may affect how blood thinners work — your dose may need adjustment
- Mounjaro can cause side effects like nausea and diarrhoea which may impact medication absorption
- Your GP may want to monitor you more closely if you're on anticoagulation therapy
There is no known direct chemical interaction between tirzepatide and standard blood thinning medications, but individual health factors matter. Your prescriber will assess whether Mounjaro is appropriate for your specific situation based on your medical history, the reason you take blood thinners, and your overall health status.
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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.
Key Safety Considerations
If you're on blood thinners and eligible for Mounjaro treatment, several points need discussion with your prescriber:
- Weight loss impact: Losing weight can naturally improve some cardiovascular markers and may affect how blood thinners work — your prescriber or anticoagulation clinic may need to review your dose
- Medication timing: Mounjaro may slow stomach emptying, potentially affecting absorption of oral medications taken at the same time — space doses appropriately
- Monitoring: You may need more frequent blood tests if taking warfarin (INR checks) or regular reviews if on direct oral anticoagulants
- Side effect management: Mounjaro's common side effects like nausea may temporarily affect oral medication absorption
Always discuss your complete medication list with your GP before starting any weight management treatment, including the Mounjaro KwikPen injection device and dose titration schedule.
- 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.
Will Mounjaro interact with warfarin?
No direct chemical interaction is known between tirzepatide and warfarin. However, weight loss can naturally improve cardiovascular markers, potentially affecting how warfarin works. Your anticoagulation clinic may need to monitor your INR (clotting time) more closely and may adjust your warfarin dose. Always inform your GP and anticoagulation service before starting Mounjaro.
Can I take Mounjaro if I'm on apixaban or other direct oral anticoagulants?
There is no known direct interaction between Mounjaro and direct oral anticoagulants like apixaban, rivaroxaban, or dabigatran. However, you must tell your prescriber you take these medications. Weight loss may improve your cardiovascular health, but your GP should monitor you to ensure your anticoagulant dose remains appropriate.
Does Mounjaro affect how blood thinners are absorbed?
Mounjaro can slow gastric emptying (how quickly food leaves the stomach), potentially affecting absorption of oral medications taken at the same time. This effect typically reduces over time. Your prescriber may recommend spacing doses or adjusting timing. Always ask your GP for specific guidance on taking your blood thinner with Mounjaro.
Will I need more blood tests if I take Mounjaro and blood thinners together?
If you're on warfarin, your anticoagulation clinic may recommend more frequent INR testing initially when starting Mounjaro, especially as weight loss progresses. For direct oral anticoagulants, monitoring depends on your individual health. Your GP will advise. Regular reviews are good practice when starting any new medication.
What should I tell my GP before starting Mounjaro if I take blood thinners?
Tell your prescriber the specific blood thinner you take (name and dose), how long you've been on it, the reason you need anticoagulation, any recent blood tests or INR results, and all other medications. Be honest about weight, health conditions, and previous medication reactions. Use our free BMI calculator to know your current BMI before your appointment — this helps your prescriber assess your Mounjaro eligibility under UK criteria.
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.