There are several reasons for anemia caused by stomach cancer: firstly, stomach cancer itself is easy to be combined with upper gastrointestinal bleeding, so it will lead to blood loss from digestive tract and lead to anemia. Secondly, gastric cancer can cause malnutrition anemia by hindering the absorption of dietary nutrients and causing the obstacle of folic acid and B12 absorption, thus leading to malnutrition anemia. After receiving radiotherapy for stomach cancer, due to the inhibitory effect of radiotherapy on bone marrow, it can also cause the decrease of hemoglobin production and lead to anemia. Other causes of anemia in gastric cancer can be the effect of certain drugs on bone marrow, the increase of destruction of red blood cells by drugs or hemolysis, so there are many reasons of anemia caused by gastric cancer, mainly bleeding, decrease of production and increase of destruction.