Colds are a common clinical condition with a high incidence in the population. After a cold, there can be systemic symptoms, such as common fever, fatigue, loss of appetite, and poor mental health. In addition, there can be respiratory symptoms, such as coughing and coughing up sputum. For patients with colds, ancillary tests, including routine blood tests and chest x-rays, can be performed to get a preliminary idea of the type of infection and the severity of the disease. For ordinary patients, there is usually no special abnormality in blood routine. For patients with more obvious symptoms of infection, there may be an increase in white blood cells, indicating the presence of a certain level of infection in the body. Further look at the neutrophil, and monocyte or lymphocyte ratios. If monocyte or lymphocyte ratios are predominantly elevated, it is more likely to be a viral cold. If the neutrophil ratio is elevated, the cold may be caused by a combination of bacterial infections. This is also a good guide for further anti-infection treatment. Therefore, it is important for patients with colds to have regular blood tests in order to understand the condition and guide further treatment.