Rehmannia glutinosa can be divided into two kinds: rehmannia glutinosa and rehmannia glutinosa. Compendium of Materia Medica states that rehmannia glutinosa will cause severe cold, but it will be used by those who are cold and blood-hot, and it will be slightly warm when cooked, but it will be used by those who are kidney-tonifying and blood-failing. Men with more yin deficiency should use Radix Rehmanniae Preparata, and women with more blood heat should use Radix Rehmanniae. Especially the prepared rhizome of rehmannia, which is used for filling bone marrow and growing muscles. It is indeed a good product to eliminate diseases and prolong life by producing essence and blood, nourishing five internal organs, benefiting eyes and ears, blackening hair and promoting blood circulation. Both Radix Rehmanniae and Radix Rehmanniae Preparata are roots of Radix Rehmanniae, a perennial herbal plant of Scrophulariaceae. Because of different processing methods, their characters and clinical applications are different. Rehmannia glutinosa, also known as dried rehmannia glutinosa, is sweet, bitter and cold in nature. It has the effects of clearing heat and cooling blood, nourishing yin and promoting fluid production, and is a medicine for clearing heat and cooling blood. It can be used for the symptoms of warm disease, such as heat entering the blood, body heat, dry mouth, crimson or red tongue, such as Qingying decoction; It is used for symptoms such as hematemesis, hematuria, metrorrhagia and metrorrhagia caused by heat in blood, such as Sisheng Pill and Rhinoceros Horn Dihuang Decoction. Used for symptoms such as yin injury caused by fever, dry tongue, thirst or polydipsia, and polydipsia due to diabetes, such as Yiwei decoction and Yuquan powder; In addition, it can also be used for constipation caused by dryness of the intestine due to heat, such as Zengye Decoction. The usual dosage is 1g～3g. Radix Rehmanniae is cold and stagnant, and it is not suitable for people with spleen deficiency and dampness stagnation and full stomach of loose stool. Rehmannia glutinosa is made of wine, Amomum villosum and dried tangerine peel. After repeated steaming, the inside and outside of Rehmannia glutinosa are black, oily and soft. Sweet and mild in nature, it has the effects of nourishing blood, nourishing yin and replenishing essence, and is an important medicine for enriching blood. For blood deficiency, chlorosis, dizziness, palpitation, insomnia, irregular menstruation, metrorrhagia and other syndromes, such as Siwu Decoction, a basic prescription for tonifying blood and regulating menstruation; It is used for kidney yin deficiency, hot flashes, night sweats, nocturnal emission, and thirst-quenching, such as Liuwei Dihuang Pill. In addition, Radix Rehmanniae Preparata is also effective for all syndromes of deficiency of essence and blood, such as backache and leg weakness, dizziness, tinnitus and deafness, premature gray hair and so on. The usual dosage is 1g～3g. Because the nature of Radix Rehmanniae Preparata is sticky, which is worse than that of Radix Rehmanniae, and hinders the digestive function, it should not be taken by people with qi stagnation, excessive phlegm, abdominal distension and pain, and eating less loose stool. This product should be used equally with spleen-invigorating and stomach-invigorating drugs such as Chenpi and Amomum villosum.