Can I take Aspirin and Dalteparin together?
Drug interaction guide
Originally published 14 Mar 2026
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Taking aspirin and dalteparin together significantly increases your risk of serious bleeding. This includes internal bleeding, such as in the stomach or brain, as well as bleeding from the gums, nosebleeds, or bruising that happens more easily than usual.
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Why this happens
Both medicines work to prevent blood clots but in different ways. Aspirin makes 'platelets' (tiny blood cells) less sticky, while dalteparin (a 'blood thinner' or anticoagulant) interferes with the proteins that help blood clot. When used together, your blood becomes much thinner than it would be with either medicine alone, making it very difficult for your body to stop any bleeding.
What you should do
Back to contentsYou should only take these two medicines together if specifically instructed to do so by a specialist doctor (such as a cardiologist or haematologist). If you are prescribed both, watch closely for signs of bleeding, such as dark 'tarry' stools, coughing up blood, or severe bruising. Seek medical advice immediately if you have a fall or a head injury. Do not take over-the-counter aspirin or similar painkillers like ibuprofen while using dalteparin.
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Important precautions
Back to contentsAsthma
Do not take aspirin if you have a history of asthma or wheezing triggered by aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs), as it can cause a severe, life-threatening asthma attack.
Active bleeding or stomach ulcers
Both medicines significantly increase your risk of severe bleeding. Do not take them if you have an active stomach ulcer or any condition causing active bleeding. Seek immediate medical help if you notice signs of internal bleeding, such as black, tarry stools or vomiting blood.
Spinal or epidural anaesthesia
If you require a spinal injection or epidural, you must inform the doctor you are using dalteparin. There is a risk of a blood clot forming in the spine (spinal haematoma), which can cause permanent paralysis.
Food and drink warnings
Back to contentsAlcohol
Drinking alcohol while taking aspirin can increase the risk of stomach irritation and bleeding. It is best to limit alcohol intake or avoid it altogether, especially if you are taking aspirin regularly.
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Using other medicines
Back to contentsTaking multiple medicines? Our Medicines Interaction Checker helps you check whether your prescriptions, over-the-counter medicines, and supplements are safe to take together. Simply search for your medicines to see potential interactions and what to do about them.
Disclaimer
This information is for general educational purposes only and should not be relied upon as a substitute for professional medical advice. Always consult your GP, pharmacist, or another qualified healthcare professional before making decisions about your medications. Individual circumstances may vary, and only a healthcare professional who knows your medical history can provide personalised guidance.
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Article history
The information on this page is written and peer reviewed by qualified clinicians.
14 Mar 2026 | Originally published

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