Coumadin, a medicine also known as warfarin, helps to prevent blood clots. Doctors may prescribe Coumadin for people who have had blood clots or have a high risk of developing blood clots, such as those with abnormal heart rhythms or other heart problems. Vitamin C and a variety of other foods can have a negative effect on warfarin's function.
Vitamin C and Coumadin
Some evidence has shown that too much vitamin C from supplements and food can decrease Coumadin's effectiveness, according to MedlinePlus. But decreasing this medication's effectiveness can put some people at greater risk of blood clots. The evidence regarding vitamin C's interaction with Coumadin remains controversial, however, according to the Linus Pauling Institute at Oregon State University. Furthermore, the University of Maryland Medical Center suggests that doses of vitamin C up to 1,000 mg per day have had no effect on Coumadin's function.
Precautions
If you are taking Coumadin, talk to your doctor about taking vitamin C supplements or eating foods rich in vitamin C. Have your blood tested regularly to check the effectiveness of Coumadin. This way, your doctor can monitor the medication's effectiveness and change your dose if necessary, notes MedlinePlus. Finally, inform your doctor of any recent vitamin C or other supplement use, because high intakes of vitamin C may interfere with the interpretation of some laboratory test results, notes the Linus Pauling Institute.
Dose
Limit your intake of vitamin C to 1 gram, or 1,000 mg, per day while taking Coumadin, recommends the Linus Pauling Institute. This amount far exceeds the minimum recommended daily intake of 90 mg for men 19 and older and 75 mg for women 19 and over, and leaves room for commonly used supplementary doses. For example, doses of 100 mg to 250 mg of vitamin C used once or twice daily can treat scurvy, and doses of 250 mg of vitamin C along with 91 mg of vitamin E twice daily can help slow the hardening of the arteries, according to MedlinePlus.
Other Interactions
A variety of foods can alter Coumadin's function in your body, including mayonnaise, cooking oils, green, leafy vegetables, cranberry juice and green tea, according to MedlinePlus Medical Encyclopedia. Some over-the-counter or prescription medications may have negative interactins with Coumadin, so discuss any medications you are taking with your doctor. Do not drink alcohol while taking Coumadin. Vitamin C can increase the side effects of estrogens and decrease the effectiveness of fluphenazine, cancer medications, AIDS medications and cholesterol-lowering medications. Vitamin C can also have minor interactions with Tylenol, aspirin, choline magnesium trisalicylate, nicardipine, nifedipine and salsalate, according to MedlinePlus.
References
- MedlinePlus Supplements: Vitamin C (Ascorbic Acid)
- MedlinePlus Medical Encyclopedia: Taking Warfarin (Coumadin)
- National Institutes of Health Office of Dietary Supplements: Vitamin C
- Linus Pauling Institute at Oregon State University: Vitamin C
- University of Maryland Medical Center: Possible Interactions with Vitamin C
- MedlinePlus Medical Encyclopedia: Vitamin C
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