If I'm on warfarin and have a headache, can I take aspirin?

If you are on warfarin it is better to take Tylenol in order to avoid a higher risk of bleeding. You should not take aspirin or any other NSAIDs without first talking to your doctor.
You should not take aspirin or any products that contain aspirin while you are taking warfarin without first talking with your doctor. Also, you should not take other painkillers such as ibuprofen (Advil, Motrin) and naproxen (Aleve, Naprosyn) without your doctor’s advice while taking warfarin. Tell your doctor and pharmacist about all the medicines (both prescription and over-the-counter), vitamins and nutritional or herbal supplements you are taking.