An 11-year-old boy sometimes says that occasionally he has no energy, and the possible clinical causes are anemia, lack of calcium and vitamin D in the body, and mental factors. 1. Anemia: there are many clinical factors related to this kind of disease, such as insufficient iron intake, reduced synthesis of hemoglobin or excessive loss of hemoglobin in the body, can cause anemia, clinical manifestations of general weakness, dizziness and so on. 2. Lack of calcium and vitamin D: Calcium is one of the most important nutrients during the development of a child. When the body lacks calcium, the development of bones will be affected, and at the same time, the excitability of the muscles will be reduced and the muscle power will be insufficient. 3. Mental factors: this is more common, the child’s school pressure or by the influence of adverse events, the mood is in a state of depression, and thus the body shows symptoms of fatigue, tiredness and other symptoms. The 11-year-old boy sometimes said that occasional lack of energy, there may also be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.