What does the term "Xu" refer to in TCM?

The term "Xu" in Traditional Chinese Medicine (TCM) refers to a deficiency state, indicating a lack of vital substances, which can include Qi, Blood, Yang, or Yin. When a patient is diagnosed with "Xu," it signifies that their body is not maintaining adequate levels of these essential elements, which can lead to various symptoms such as fatigue, weakness, paleness, or feelings of coldness, depending on which specific area is deficient.

Each of these vital substances plays a critical role in maintaining health and balance within the body. For example, Qi is the vital energy that circulates throughout the body, Blood nourishes and moistens the organs and tissues, Yang represents the active, warming aspect of energy, and Yin embodies the cooling, nourishing aspect. A deficiency in any of these can lead to a wide array of health issues, making the understanding of "Xu" fundamental in TCM diagnostics and treatment strategies.