The source is from the root of Rehmannia glutinosa Libosch., family Scrophulariaceae. The medicinal material is mainly produced in the areas of Henan, Hebei, and Inner Mongolia, etc. Mter dried, it is prepared by steaming with wine, Sharen ( Fructus Amomi) and Jupi (Pericarpium Citri Tangerinae), and drying itself repeatedly until it becomes black internally and externally, has the quality of softness and stickiness. It is cut into slices for medication.

Medicinal Properties: Sweet in flavor, slightly warm in nature and attributive to the liver and kidney meridians.

Actions: Enrich the blood and nourish yin, and supplement the essence.

Application
1. It is indicated for blood deficiency manifested as sallow complexion, dizziness, palpitation, irregular menstruation and metrorrhagia and metrostaxis, it is usually combined with Danggui ( Radix Angelicae Sinensis ), Baishaoyao (Radix Paeoniae Alba), Chuanxiong (Rhizoma Chuanxiong), etc., such as Siwu Tang (Decoction).
2. For deficiency of liver-yin and kidney-yin manifested as hectic fever, night sweat, emission and diabetes, it is usually used together with Shanyao (Rhizoma Dioscoreae), Shanzhuyu (Fructus Corni), etc., such as Liuwei Dihuang Wan (Bolus). For insufficiency of kidney-yin resulting in preponderant deficiency-fire with low fever and obvious night sweat, used together with Zhimu ( Rhizoma Anemarrhenae ), Huangbai ( Cortex Phellodendri), Guiban (Plastrum Testudinis) and others that can nourish yin to clear fire, such as Da Buyin Wan Bolus.
3. For insufficiency of the essence and blood resulting in soreness of loins and knees, dizziness, tinnitus, deafness, poor vision, premature whitening of hair, etc., it is usually used with Heshouwu (Radix Polygoni Multiflori), Nfizhenzi ( Fructus Ligustri Lucidi ), Hanliancao (Herba Ecliptae ), and Shanzhuyu ( Fructus Corni ), etc..

Usage and Dosage:
10 -15 g is used in decoction for oral use.

Notes:
It is sticky and rich in property and tends to obstruct digestion, therefore, it is not suitable for cases with excessive sputum, fullness in the epigastric region, poor appetite and loose stool.

Explanation:
Shengdihuang ( Radix Rehmanniae ) and Shudihuang ( Radix Rehmanniae Praeparata ) are different in processing, so their actions are also different. Shengdihuang (Radix Rehmanniae) is effective in clearing away heat and cooling the blood, promoting the production of the body fluids, and mostly used in treating seasonal febrile disease resulting in heat invading yingfen and xuefen, general fever and eruption, bleeding due to bloodheat, thirst and constipation due to consumption of the body fluids caused by yin-deficiency. Whereas the nature of Shudihuang (Radix Rehmanniae Praeparata ) is warm that is changed from the cold nature of Shengdihuang (Radix Rehmanniae) so that Shudihuang (Radix Rehmanniae Praeparata ) is effective in enriching the blood and nourishing yin, it is usually used in treating syndromes of deficiency of yin and the blood, and insufficiency of essence.