Warfarin and Aspirin Interaction
Drug interaction information between Warfarin and Aspirin.
Warfarin and Aspirin have a documented moderate interaction in FDA labeling.
FDA drug labeling documents a moderate-severity interaction between Warfarin and Aspirin. Major interactions are generally avoided, moderate ones may need monitoring or a dose adjustment, and minor ones are usually low-risk. This page shows the documented mechanism and guidance. Label-documented interactions are not a complete safety review, so always confirm your own medications with a pharmacist or doctor. Educational information, not medical advice.
How They Interact
Aspirin is an antiplatelet drug that adds to the blood-thinning effect of warfarin. Taking both together significantly increases your chance of having a serious bleeding event.
What To Do
Talk to your doctor before taking these two drugs together. They may need to adjust your dosage or check your blood levels more frequently.
Warfarin Also Interacts With
- Fluoxetine major
- Tamoxifen major
- Ibuprofen moderate
- Diclofenac moderate
- Desvenlafaxine moderate
Aspirin Also Interacts With
- Atenolol major
- Fluoxetine major
- Ibandronate major
- Alendronate moderate
- Apixaban moderate
Frequently Asked Questions
Can I take Warfarin and Aspirin together?
This is a moderate interaction. Talk to your doctor before taking these two drugs together. They may need to adjust your dosage or check your blood levels more frequently.
How serious is the interaction between Warfarin and Aspirin?
This interaction is classified as "moderate" severity by the FDA. Moderate interactions may worsen your condition or change how your medications work.
Why do Warfarin and Aspirin interact?
Aspirin is an antiplatelet drug that adds to the blood-thinning effect of warfarin. Taking both together significantly increases your chance of having a serious bleeding event.
Understanding the Warfarin and Aspirin Interaction
FDA-approved prescribing information for these two drugs flags their combination as a moderate-severity interaction. Warfarin belongs to the Vitamin K Antagonist (Anticoagulant) class and Aspirin belongs to the Antiplatelet / NSAID class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Aspirin is an antiplatelet drug that adds to the blood-thinning effect of warfarin. Severity tiers matter: major flags generally advise avoidance, moderate flags often require monitoring or dose adjustment, and minor flags may only call for awareness.
Context around a specific patient determines real-world impact. Warfarin has 163 total documented interactions on file in this dataset, and Aspirin has 47. Each additional medication compounds the interaction surface, which is why pharmacists run full-profile checks rather than evaluating one pair at a time. FDA-derived guidance for this pair is: Talk to your doctor before taking these two drugs together. Timing of doses, renal and hepatic function, age, and other concurrent prescriptions all shape whether a labeled interaction matters clinically.
An interaction flag is not a verdict. A large share of labeled interactions are managed routinely in clinical practice, the fix may be as simple as spacing doses or adding a monitoring test. Others require the prescriber to choose a different medication entirely. This page surfaces FDA-sourced labeling and openFDA data for educational purposes only; it is not medical advice and cannot account for your full clinical picture. Never start, stop, or adjust either Warfarin or Aspirin based on a web page, speak with your prescriber or pharmacist before making any change.
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. Always consult your healthcare provider about drug interactions.
Read our methodology - how this data is sourced, computed, and verified.