Some foods that thicken blood are parsley, kale, spinach, collard greens and asparagus, all which have high levels of vitamin K, states DVT Lite. In its supplement form, vitamin K is prescribed to people who have thin blood.
Foods with healthy cultures and bacteria also contain high amounts of vitamin K, according to DVT Lite. These cultures and bacteria primarily come from products such as yogurt, buttermilk and sourdough bread.
Some more foods that help thicken blood are chicken livers, sunflower seeds, cashews, soybeans and barley, states Diet and Nutrition. These foods are all high in copper which is important for blood composition. Copper also contains iron, which produces hemoglobin. People who don't get enough copper can suffer from anemia and thrombocytopenia.
Calcium also thickens blood, states DVT Lite, and some foods that contain high amounts of it are milk, mozzarella cheese, tofu and almonds. Folic acid and B-12 are also important in thickening blood, and some good sources include meat, poultry and fish, states Nutrition and Diet.
People who take warfarin or other blood thinners should avoid consuming too much vitamin K because it can lead to dangerous amounts of clotting, states Drugs.com. Patients should not have too little vitamin K because it can lead to too much bleeding.