Sleepy during the day but unable to sleep at night is usually a case of sleep inversion. Sleep inversion is also a kind of sleep disorder, belongs to the category of insomnia, the cause is mainly related to sleep rhythm disorder. The rhythm of sleep is mainly regulated by melatonin, normal melatonin secretion in accordance with the day and night, generally at night 2-3 o’clock, darkness without light is the peak of melatonin secretion. So if you often stay up late or like to sleep with the lights on, it is easy to produce melatonin secretion disorder, affecting the normal sleep. Once this happens, it is recommended to try to avoid sleeping during the day and adjust the sleep time to night. If the independent adjustment is not effective, you also need to take medication, preferred melatonin receptor modulating drugs, such as trazodone, agomelatine.