Clotting is the ability of the blood to become a clot – that is, to thicken and solidify. This process occurs by the action of combination of platelets and clotting factors. The tendency of the blood to clot has to be held in careful balance – if it clots to easily, it will block of the flow of blood through vessels. If it is too thin, then if a vessel is broken or injured (such as in a cut or bruise), then blood will continue to flow out and never stop. This balance can be deliberately or accidentally changed by certain unusual changes in the diet or prescription drugs. People also may have an uneven balance due to their genetic make-up.