Cold fever at night and no fever during the day is mainly considered to be related to the characteristics of the virus that causes colds, and may also be related to the concentration of medication during the day and the decrease in blood concentration at night. 1.Virus active characteristics Colds are usually caused by viral infections, as viruses have their living habits, i.e., slower reproduction during the day and faster reproduction at night. Due to the rapid reproduction of the virus at night, it can produce more excretions, i.e. toxins, which become exogenous thermogenic sources, and stimulate the thermoregulatory center to be impaired, which will cause the body temperature to rise, thus leading to fever at night. The main reason for the lack of fever during the day is that the virus reproduces more slowly and produces less toxins. 2. Decrease in blood drug concentration at night Cold fever at night and no fever during the day may also be related to the application of drugs. When the drug in the blood maintains an effective concentration or more, it can play a role in the efficacy of the drug. Some drugs are used in insufficient dosage, so that the blood concentration at night has dropped to the ineffective stage, and not timely additional dose, can lead to fever symptoms. Therefore, it is necessary to use drugs according to the half-life of drugs. Cold is one of the most common respiratory infections in clinical practice. When you have a cold, you should drink plenty of boiled water, rest more, and increase or decrease clothing at the right time. If you have a cold with fever at night but not during the day, you should go to the hospital in time and do relevant auxiliary tests such as routine blood test, C-reactive protein, etc. in order to clarify the cause of the disease and guide the treatment, and do not treat it without authorization, so as to avoid aggravation of the disease and cause adverse outcomes.