Although vitamin B-12 and warfarin are not likely to interact with each other, they may negatively interact with other vitamins and supplements. Warfarin may also cause adverse side effects in some individuals, some of which can be life-threatening. Discuss the potential risks and benefits with a doctor before taking any new medication or supplement.
Vitamin B-12 is naturally present in certain foods and is also available as a dietary supplement and a prescription medication. This vitamin is necessary for proper formation of red blood cells, DNA synthesis and neurological function. Although many people get enough vitamin B-12 by eating a healthy and well-balanced diet, some may benefit from extra supplementation. Older adults or those with a certain medical condition, such as a gastrointestinal disorder or pernicious anemia, fall into this category. Strict vegetarians or vegans may also need B-12 supplements, especially during pregnancy. Vitamin B-12 does not have a tolerable upper intake level. This means side effects from the vitamin are unlikely, even when you take large doses.
Warfarin is a prescription blood-thinning medication. It prevents blood clots from forming or growing. Doctors typically prescribe this medication for individuals with prosthetic heart valves, those who have suffered a heart attack and those who have certain types of irregular heartbeats. Common side effects of the medication include gas, tiredness, pale skin, feeling cold or having chills, change in the way things taste and hair loss. It also has the potential to cause necrosis or gangrene. If you notice any unusual changes after taking this medication, call a doctor. The medication also negatively interacts with many supplements and medications, so it is essential that you tell your doctor about all of your current medications and supplements before taking warfarin.
It is unlikely that B-12 and warfarin will negatively interact with each other, according to the Drugs.com Interaction Checker. However, just because an interaction between the two is not known doesn't mean one doesn't exist. Always report any unusual side effects to a doctor while taking vitamin B-12 with warfarin. Anti-convulsants, chemotherapy medications, certain gout medications, H2 blockers, proton pump inhibitors, bile acid sequestrants, diabetes medications and antibiotics may interact negatively with both vitamin B-12 and warfarin. Warfarin may also negatively interact with aspirin, nonsteroidal anti-inflammatory drugs, heparin, cold or allergy medications, antidepressants, oral contraceptives, thyroid medications, painkillers, heart medications, streptokinase, urokinase and ticlopidine. It also interacts with herbal supplements, such as bromelains, cranberry products, dong quai, garlic, ginkgo biloba, St. John's wort, coenzyme Q10, ginseng and dashin.
Whether taken with vitamin B-12 or not, warfarin may cause serious and life-threatening reactions. The medication may cause severe bleeding that can result in death. This is more likely for people over 65 years old and for those who take large doses of the medication. It is also more likely for people who regularly participate in sports or activities that may result in serious injuries. If you experience any bleeding from a cut that does not stop in the usual amount of time, call a doctor. Also call your doctor if you experience nosebleeds, bleeding from your gums, coughing up or vomiting blood, increased menstrual flow or unusual vaginal bleeding, headaches, dizziness, weakness, pain, swelling or discomfort.