Deficiency fire is a Chinese medical term for a disease in Chinese medicine. There is a difference between real and virtual fire, and deficiency fire is relative to real fire. Any deficiency caused by physical weakness, true yin deficiency or true yang exhaustion and manifested as deficiency hyperactivity, belongs to the category of deficiency fire. There are two sources of deficiency fire, one is the deficiency of yin can fever, this is due to the loss of true yin, water does not control the fire; secondly, the deficiency of yang can also fever, this is due to the defeat of the Yang, fire does not return to the original source, this source of disease is also the second. Deficiency fire is commonly seen clinically in what modern medicine calls functional hypothermia, blood diseases, connective tissue diseases, endocrine diseases, advanced tumors, after radiation therapy and chemotherapy for tumors, or other chronic infectious diseases.