Nocturnal fever is commonly associated with infectious diseases such as bacterial infections, viral infections, and mycoplasma infections. It can also be seen in immune system disorders. It is also important to rule out the possibility that the high temperature is caused by too thick a blanket at night. Fever is most commonly associated with infectious diseases, such as tuberculosis caused by Mycobacterium tuberculosis infection, which often results in a low fever at night; respiratory diseases caused by Streptococcus pneumoniae infection, respiratory syncytial virus, and Mycoplasma pneumoniae infection can be accompanied by fever. Inflammation caused by pathogenic bacteria invading the digestive system, the blood system, the urinary system, etc., can also present with fever. In addition to infectious factors, consider fever caused by immune disorders, commonly seen in rheumatic diseases. Excluding environmental factors such as due to improper measurements or too thick a blanket at night, it is recommended to seek medical attention if nighttime fever persists so as not to delay the condition.