Although Blood in appearance is similar in TCM and Western medicine, it cannot be regarded in the same manner. In TCM, Blood is a Yin substance, so it depends on Qi to be generated and distributed. And Blood Deficiency is not equal to anemia. In most cases in TCM, anemia should be diagnosed as Deficiency of both Qi and Blood.

Blood is mainly composed of Nutritive Qi and Body Fluids, which come from the refined food transformed and transported by the Spleen and Stomach. So the Spleen and Stomach are also known as "the source of Qi and Blood", and the quality of the nutrients taken in, as well as the functional states of the Spleen and Stomach, influence directly the formation of Blood. The Essence stored in the Kidney can also be transformed into Blood by two methods. First, Kidney Essence and Liver Blood can be transformed into each other so that the Blood of the whole body is supplemented. Second, Kidney Essence supplies bones with marrow, which not only nourishes the bones but also generates Blood

The main function of Blood is to nourish the whole body. Blood circulates ceaselessly through the vessels, by which it is carried to Zangfu Organs internally and to the skin, muscles, tendons and bones externally, to both nourish and moisten. Compared with Qi, Blood is a Yin substance which functions to support the body physique. Therefore, it serves as a Nutritive substance of the body. When the Blood is sufficient, there is a rosy and bright face, strong and well-developed muscles, and lustrous skin and hair. On the other hand, Deficiency of Blood will lead to withered hair and skin, atrophy and convulsion of tendons, thin muscles and weak Zangfu Organs.

Blood is also regarded as the material basis for mental activities, which are controlled by the Heart. As the Heart is in charge of Blood and vessels, the mental activities controlled by the Heart mainly take Heart Blood for their material basis. For this reason, sufficient Blood often exhibits as full vigor, perfect consciousness, keen perception, etc., while Deficiency of Blood usually leads to listlessness, insomnia, dream-disturbed sleep, dysphoria, or even vagueness of the Mind and other mental disorders.v