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Shengdi (Rehmanniae Radix), with a bitter and sweet taste, is cold in nature, heavy in quality, and belongs to the Yin category. It enters the Hand-Shaoyin Heart Meridian and the Hand-Taiyin Lung Meridian. It cools down fire in the head and face, clears heat from the Lungs and Liver, and can also serve as the Jun Herb (the principal herb in a prescription). Its efficacy specializes in cooling blood and stopping bleeding; it is also adept at treating metal wounds, stabilizing fetal Qi, unblocking meridians, and stopping metrorrhagia and uterine bleeding, all with miraculous effects. However, due to its cold nature, it is not suitable for frequent use by those with cold Spleen and Stomach. Since Shengdi excels at cooling blood, for conditions where hot blood moves recklessly, resulting in hematemesis (vomiting blood), epistaxis (nosebleed), or lower body bleeding, it should be used as the Jun Herb. By adding Jingjie (Schizonepetae Herba) to guide blood back into the vessels, and adding Sanqi root powder (Notoginseng Radix et Rhizoma) to block the bleeding pathway, what heat would remain uneliminated and what bleeding would fail to stop? Nevertheless, this herb can be used in large doses but not frequently; it can be used temporarily but not for a long duration. When bleeding occurs, the condition is often urgent, necessitating the heavy use of Shengdi to cool blood and stop bleeding. Once the bleeding stops, one should switch to warming and tonifying formulas, rather than continuing with Shengdi. People today do not understand this principle; amazed by Shengdi's miraculous hemostatic effect, they regard it as a panacea, decocting and taking it daily. Over time, this causes the Spleen and Stomach to become too cold, inevitably leading to diarrhea, exhaustion of Yuan Qi (Original Qi), and the recurrence of bleeding. They fail to realize that excessive use of Shengdi leads them to suspect insufficient dosage, causing them to increase the dose further, even up to death without awakening, which is truly pitiable.

One asks: Shengdi and Shudi (Prepared Rehmanniae Radix) are from the same source, yet their cold and warm natures differ. Does Shengdi transform into Shudi when decocted in soup? The answer is: If Shengdi is not processed into Shudi beforehand, its taste is bitter, and bitterness implies coldness. If Shengdi has been processed into Shudi, its taste becomes sweet, and sweetness implies warmth. How can they be compared? It is like a person: initially unrefined, their nature is rigid; after cultivation and nurturing, their nature becomes gentle. Is it not so for Shengdi and Shudi?

One asks: Shengdi cools blood to stop bleeding, making it a miraculous drug for saving lives. I see people who, after using Shengdi to stop bleeding, dare not use it again and switch to other herbs, yet still vomit blood. However, upon taking Shengdi, the bleeding stops immediately. How can it be said that Shengdi is unsuitable for long-term use? The response is: After stopping bleeding with Shengdi, if switching to other herbs results in continued hematemesis, it is not because Shengdi was not used, but because the substituted herbs were inappropriate. After stopping bleeding, blood must be replenished, but this is difficult. Blood-tonifying herbs are invariably warm, yet after hematemesis, warmth is most contraindicated, as warm properties may agitate the boiling blood. Blood-tonifying herbs are invariably moving, yet after hematemesis, movement is most contraindicated, as moving Qi may urge blood to flow out. So, after using Shengdi to stop bleeding, what herb should be used for follow-up treatment? Liuwei Dihuang Wan (Six-Ingredient Pill with Rehmannia) added with Wuweizi (Schisandrae Fructus) and Maidong (Ophiopogonis Radix) is neutral and not hot, calm and non-moving. Taking it causes Kidney Water to rise and Heart Fire to descend, eliminating the worry of recurrence. Why insist on the necessity of taking Shengdi?

One doubts: Although Shengdi is cool, it is not extremely cold. It seems suitable for treating deficiency-heat diseases, so why is its prohibition so strict? One does not know that Shengdi’s coolness penetrates not only the Stomach but also the Spleen, and not only the Spleen but also the Kidneys. Therefore, long-term use damages both the Spleen and Kidneys, often leading to severe diarrhea (Da Jia Zhi Xie), so it must be used with caution.

One doubts: Shengdi’s hemostatic effect is miraculous, and it contains tonification within its purging action, seemingly comparable to Xuanshen (Scrophulariae Radix). However, Xuanshen can be used in heavy doses, whereas Shengdi should strictly be used in light doses. This is because Shengdi has a sinking and Yin nature; cooling blood is its strength, while clearing fire is its weakness. Unlike Xuanshen, which clears floating fire and nourishes dried-up fluids, Shengdi cools blood so that although bleeding stops, circulation halts. Shengdi cannot clear fire, so fire tends to flare up and remains restless; over time, fire rises upward, and blood boils along with it.

One doubts: Shengdi is cold and cool, capable of stopping bleeding. Is it because blood stops when cooled? Or because blood stops when tonified? Shengdi is cool yet contains tonification; blood stops when cooled and also when tonified. Blood requires coolness to curb its flaming upward trend, and it requires tonification to achieve harmonious balance (Ji Ji). Thus, Shengdi’s miraculous hemostatic achievement lies precisely in its combination of cooling and tonification.

One doubts: Shengdi clears heat from the Lungs and Liver. Since both Lungs and Liver belong to Yin, and Yin tonification acts slowly, long-term use seems appropriate. Why is it said that Shengdi can only be used temporarily and not commonly? The answer is: Shengdi clears heat from the Lungs and Liver only for a temporary period. Lung and Liver fire is mostly excess in the early stages and mostly deficiency in chronic illness. Shengdi clears initial excess heat, transforming heat into cold; however, clearing chronic deficiency heat increases heat further. Excess fire subsides with cold, but deficiency fire flares up with cold. Therefore, Shengdi can only be used temporarily for a short time and must absolutely not be used for a long duration.