Pallor in a 13-year-old girl may be caused by non-disease factors, such as fear, or by disease factors, such as anemia, hypoglycemic episodes, and upright hypotension. 1. Non-disease factors: (1) Fear: If a 13-year-old girl has a nervous, fearful experience, the capillary blood vessels in her face contract, there will be a transient pallor, which can be relieved after a period of rest. 2. Disease factors: (1) Anemia: if a 13-year-old girl suffers from aplastic anemia, iron deficiency anemia, hemolytic anemia and other diseases, anemia can occur due to insufficient or reduced red blood cell production, excessive destruction of red blood cells and other factors, resulting in the girl’s weakness, pallor, memory loss and other symptoms. (2) Hypoglycemic attack: If a 13-year-old girl is chronically hungry and malnourished, it can trigger a hypoglycemic attack, resulting in pallor, palpitations (rapid heartbeat, often accompanied by panic), sweating, and, in severe cases, loss of consciousness. (3) Upright hypotension: If a 13-year-old girl suddenly switches from lying down or squatting to standing, upright hypotension can be triggered, resulting in dizziness, blackness and pallor. In addition, there are many other causes can cause 13-year-old girl pale, it is recommended to go to the hospital in a timely manner, to rule out non-disease factors, and then receive treatment as soon as possible.