The reasons for wanting to sleep during the day are as follows: 1, the most common reason is due to lack of sleep at night, or poor sleep quality, resulting in the body and brain do not get sufficient rest, it will be easy to sleepy during the day, lack of energy, want to sleep; 2, long-term late nights lead to changes in the sleep rhythm, the night will be very mental, the day will be very sleepy, usually need a period of conditioning, as well as taking melatonin and other 3, there are some drugs can cause the symptoms of sleepiness during the day, the most typical is anti-allergy drugs, antihistamines, paracetamol, also known as chlorpheniramine maleate, has a very obvious side effect of making people drowsy, sleepy, this drug component exists in a variety of anti-cold drugs, so many cold drugs after taking will lead to the symptoms of sleepiness during the day.