Vitamin K
If you take the drug warfarin – used to treat and prevent blood clots – be aware of how much vitamin K you take in. It can make the blood thinner less effective and put you at higher risk of a dangerous blood clot. Broccoli, Brussels sprouts, kale, parsley, and spinach are some of the most common foods high in vitamin K. Try to eat the same amount of these foods every day so the level of warfarin in your blood stays the same.