People feel tired for the following reasons: First, the physical work intensity is too heavy, the body does not get enough rest, the body energy consumption is too much, resulting in a lack of energy in the body, so people feel particularly tired, at this time still feel the need to rest, and sometimes there is a sense of hunger. Second, work and study pressure is too great, mental overstress, long time too much mental fatigue, people will feel especially tired and weak. Third, disease factors, most of the diseases will make a person tired and weak, there is a feeling of feeling tired, such as colds, tuberculosis, anemia, liver and kidney disease, hypothyroidism, a variety of tumors, heart disease and so on. When a person has no physical exertion and no mental stress, but feels tired without any reason, he should be alert to whether he suffers from some kind of disease, especially the old people should be alert to heart diseases and tumors, and he should go to the hospital in time to improve the physical health checkup.