DrugPair interaction guide

Warfarin and Aspirin

Both warfarin and aspirin affect clotting. Together they can substantially raise the risk of serious bleeding, including internal bleeding.

Written by DrugPair Editorial Team. Updated 16 July 2026.

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Major interaction

Do not combine without direct medical supervision.

What you need to know

Aspirin inhibits platelet function while warfarin reduces clotting factor production. Combined, they amplify each other's effects. In certain cardiac conditions doctors do prescribe both together, but only with close monitoring. Self-medicating with aspirin while on warfarin is not safe without medical guidance.

What to do

Do not add aspirin to your warfarin regimen without explicit medical approval.

If your doctor prescribes both, get clear instructions on doses and warning signs to watch for.

Check all OTC medicines — many cold and pain products contain aspirin.

When to call your doctor

Any unexpected bleeding: gums, nose, cuts that will not stop, blood in urine or stool.

Severe headache, dizziness, or sudden weakness.

Severe symptoms? Call 911 (US) or Poison Control 1-800-222-1222

Sources

Warfarin: Drug InformationNIH MedlinePlus. Accessed 2026-07-16.As You Age: You and Your MedicinesU.S. Food and Drug Administration. Accessed 2026-07-16.

Source databases can disagree or omit an interaction. Report an error.

DrugPair provides educational safety information only and is not a substitute for professional medical advice. Always ask a doctor or pharmacist before changing medicines, supplements, food, drinks, or prescription timing.

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