According to MedlinePlus, patients taking Coumadin should not drink alcohol because it sometimes alters the way the medication functions. Coumadin, a brand name for warfarin, reduces the possibility of blot clots forming.
MedlinePlus warns that Coumadin causes people to bleed very easily, even from ordinary activities. Therefore, patients should avoid circumstances that potentially cause injuries, such as contact sports. Patients should be on the lookout for bleeding gums, bloody urine or stools, nosebleeds, dark bruising or bloody vomit. Women taking Coumadin sometimes have very heavy periods. Along with these symptoms, people on the drug need to report headaches, dizziness, falls, fever, illnesses or pregnancy to their doctors.