Feeling tired after a long period of time may be caused by frequent or too long coitus, anemia, and basic diseases. 1. Frequent or long coitus: If the coitus is frequent or too long, it will lead to physical exertion, the body appears to want to rest signals, resulting in a very tired after coitus, to reduce the frequency of coitus, pay attention to rest, generally can be relieved by themselves. 2. Anemia: when the patient’s blood red blood cells are low, there is anemia, because in the process of intercourse will consume a lot of energy and oxygen, will make the body appear insufficient blood supply, which leads to a long period of time the patient feels very tired. 3. Basic diseases: If the patient himself suffers from basic diseases, such as diabetes, etc., resulting in the body can not support the supply of energy in the process of coitus, and then when the energy consumption is too much, the situation of feeling very tired for a long time. A long time after the same bed feel very tired for many reasons, it is recommended to go to the hospital in a timely manner, under the diagnosis of the doctor, according to the patient’s condition, to take targeted treatment, life should pay attention to rest, avoid overwork, appropriate exercise, improve their quality.