I don't know what "emergency" in this context is. With regard to vitamin C, it can have an effect on INR but can be taken safely if it is taken with the same rigor that Coumadin is taken. My husband takes his vitamin C each and every day, just as he takes his anticoagulant.
The problem with taking vitamins that affect anticoagulation is lack of consistency. People know that Coumadin is necessary daily but maynot accord vitamins the same awareness. Dosage is also important. What is the strength of the Vitamin C that you are considering?
Regards,
Blanche
P.S. Hubby's Doc recommended B Vitamins 16 years ago. No problems there.