Usually the causes of low fever followed by high fever in the human body are as follows: 1. The most common factors are infectious factors, such as when the body is infected by bacteria, viruses, pathogenic microorganisms, intestines such as fungi, etc., there will be a case of low fever followed by high fever in the body temperature. If the body is combined with bacterial infections, there will also be a low fever followed by high fever; when the body is infected with bacteria and at the same time infected with viruses, this will also occur when the body temperature is low and then high; if the body is infected with viruses and at the same time combined with fungal infections, there will also be a low temperature followed by high. 2, non-infectious factors, such as patients suffering from tumors, connective tissue diseases, or immune deficiency caused by Rheumatic diseases, the initial stage of the disease and the exacerbation of the disease, there will be a low fever and then high fever, which is a manifestation of the aggravation of the disease.