Patients should talk to their physician before taking anticoagulants if they have been diagnosed with any of the following conditions, because the medication could potentially lead to uncontrolled bleeding:

• Infections of the heart (e.g., bacterial endocarditis).
  
  
• Vitamin K deficiency. Patients with this deficiency may still be prescribed warfarin but at a very low dose. It is very important for patients on anticoagulants to maintain a fairly consistent level of vitamin K in their diet.
  
  
• Bleeding disorders.
  
  
• Past or current ulcer (stomach or duodenal). Ulcer patients are often prescribed anticoagulants after the risks and benefits have been discussed with their physician. Although a past history of gastrointestinal bleeding rarely interferes with taking the medications, patients who have current gastrointestinal bleeding cannot take them.
  
  
• Aneurysm (swelling or bulging in part of the wall of a blood vessel). Anticoagulants can be used with caution in patients with certain types of aneurysms.
  
  
• Cancer of the internal organs. Certain cancers can cause bleeding.
  
  
• Recent surgery or spinal anesthesia.
  
  
• Pregnancy. Pregnant women cannot take warfarin but can take other anticoagulants, such as heparin.