The most common cause of anemia is chronic blood loss. Since anemia develops gradually over a longer period of time, by the time the symptoms of anemia appear, the primary disease has been present for some time. For example, ulcer diseases and tumors in the peptic tract are likely to cause anemia. When it comes to the relationship between gastric cancer and anemia, we can talk about it from two major aspects. First, anemia may induce gastric cancer. Pernicious anemia itself is listed as one of the precancerous lesions of gastric cancer. Anemia is often accompanied by iron deficiency, which tends to lead to chronic atrophy of the mucosa of the tongue, esophagus, stomach and small intestine, making stomach acid too low or lacking. The consequence is that a large number of bacteria accumulate and multiply in the stomach and cause the nitrate ingested into the body to synthesize strong carcinogen nitrosamines with amines in the stomach. In addition, gastric cancer can cause anemia through the following reasons. 1.Blood loss anemia is usually caused by acute and chronic blood loss on the surface of the lesion or invasion of the cancer nest to the blood vessels of the stomach wall, and can also be caused by massive blood loss from the rupture of advanced gastric tumor. 2.Malnutrition anemia The digestion and absorption function of gastric cancer patients will be reduced to different degrees, resulting in the impaired intake of essential nutrients such as iron, folic acid, vitamins and protein for hematopoiesis. 3. Cachexia caused by advanced gastric cancer Furthermore, anemia does not only occur in progressive gastric cancer. Recently, the Department of Gastrointestinal Surgery of the Third Hospital of Harbin Medical University successfully treated a patient with upper gastrointestinal bleeding, who had a total of nearly 5000ml of bleeding in three times, which was equivalent to replacing the blood of the whole body, and was later confirmed by surgery and pathology as early gastric cancer (intra-mucosal cancer) with a diameter of 2mm. The related epidemiological survey showed that 44.1% of the patients had anemia at the initial diagnosis, 20.5% had mild anemia, 12.3% had moderate anemia, and 11.2% had severe anemia. The percentage of male and female patients with anemia was 36.5% and 61.6%, respectively. Among all gastric cancer patients, the proportions of anemia in stage I, II, III and IV gastric cancer patients were 27.2%, 45.1%, 51.4% and 47.2%, respectively. Young anemic patients accounted for 51.6%, middle-aged 38.7% and elderly 48.9%. It can be seen that the incidence of tumor-related anemia among gastric cancer patients in China is high, showing the trend that women are more common than men, the proportion of young patients with anemia is higher than that of elderly patients with anemia, and the proportion of elderly patients with anemia is higher than that of middle-aged patients. Therefore, once anemia occurs, do not take blood supplements without authorization, but go to a regular hospital immediately to find the cause of the disease. The reason is that after anemic patients have taken blood-supplementing drugs, the symptoms of anemia will improve to some extent, masking the primary disease and misleading the diagnosis.