Some of the foods that make blood thick include spinach, collard greens, asparagus, cauliflower, leeks, celery and turnip greens. All of these foods include Vitamin K, which is the fat-soluble vitamin that helps blood clot.
There are no known adverse effects associated with ingesting too much vitamin K from food or from organic supplements. However, if a person is taking blood-thinning medications for any reason, he should limit the amount of vitamin K he takes, as the vitamin could affect the blood-thinning medicine. Some of the indications that a person does not have enough vitamin K include nose bleeds, blood in the urine and bleeding gums.