大泻火
甘苦大寒，入心肾。泻丙火（小肠为丙火，心与小肠相表里，导赤散与木通同用），清
燥金（胃、大肠火），消瘀通经，平诸血逆。治吐衄崩中（唾血者，血随唾出；咯血者，随
痰咯出，或带血丝，出肾经及肺经。自两胁逆上吐出者，属肝经。衄血者，血溢于脑，从鼻
而出；咳血者，咳出痰内有血，并属肺经。吐出呕出成盆成碗者，属胃经。经漏不止曰崩，
血热则妄行，宜以此凉之。虚人忌用，用于干地黄可也），伤寒阳强，痘症大热（痘症用之
甚多，本草未载）。多服损胃。
生掘鲜者，捣汁饮之，或用酒制，则不伤胃。生则寒，干则凉，热则温（故分为三条，
以便施用）。
补阴，凉血
甘苦而寒，沉阴而降。入手足少阴（心、肾）、厥阴（心包、肝），及手太阳经（小肠）。
滋阴退阳，生血凉血。
治血虚发热（经曰∶阴虚生内热），劳伤咳嗽（咳嗽阴虚者，地黄丸为要药，亦能除痰。
丹溪曰∶久病阴火上升，津液生痰不生血，宜补血以制相火，其痰自除），痿痹惊悸（有
触而心动曰惊，无惊而自动曰悸，即怔忡也。有因心虚火动者，有因肝虚胆怯者，有因水停
心下者，火畏水故悸也。地黄能交心肾而益肝胆，亦能行水，故治之）。吐衄尿血（痛为血
淋，不痛为尿血。由心、肾气结，或忧思、房劳所致，多属虚寒，不可专作热治）血晕崩（经
曰∶阴虚阳搏谓之崩），足下热痛，折跌绝筋（生地一斤，瓜姜糟一斤，生姜四两，炒熟，
伤折处，冷则易之。又生地汁三分，酒一升半，煮服，下扑损瘀血），填骨髓，长肌肉，
利大小便，调经安胎，又能杀虫。治心腹急痛（《海上方》∶捣汁和面作 饪食，能利出虫，
忌用盐。《本草汇》曰∶丹溪云气病补血，虽不中病，亦无害也。不知血药属阴，其性凝滞，
若胃虚气弱之人，过服归地等剂，反致痞闷，饮食减少，变证百出，至死不悟，岂不惜哉！
大抵血虚，固不可专补其气，而气虚亦不可徒补其血也。凡劳病，阳虚宜四君补气；阴虚宜
四物补血；阴阳俱虚者，宜合用，名八珍汤）。
江浙生者，南方阳气力微；北方生者，纯阴力大，以怀庆肥大菊花心者良。酒制则上行
外行，姜制则不泥膈。恶贝母。畏芜荑。忌莱菔、葱、蒜、铜铁器。得酒、门冬、丹皮、当
归良。
大泻火
味甘、苦，性大寒，归心经和肾经。清泻丙火（小肠属丙火，心与小肠互为表里，导赤散中与木通同用），清燥金（指胃和大肠之火），消除瘀血并疏通经脉，平息各种血气上逆。治疗吐血、鼻衄及崩漏（唾血，指血液随唾液而出；咯血，指随痰液咳出，或带有血丝，病位在肾经和肺经。从两胁向上逆冲而吐出的，属于肝经。衄血，指血液溢出脑部，从鼻腔流出；咳血，指咳嗽时痰中带血，均属于肺经。吐出或呕出量多如盆碗的，属于胃经。月经淋漓不尽称为崩，因血热导致血液妄行，适宜用此药凉血止血。体质虚弱者忌用，若需使用可用干地黄代替），伤寒病中阳气亢盛无制，痘疹重症高热（治疗痘疹时常使用此药，但《本草》古籍中未记载）。服用过多会损伤胃气。
若是刚挖掘的新鲜生地黄，捣烂取汁饮用，或用酒炮制，则不伤胃气。生品性寒，干品性凉，熟品性温（因此分为三种规格，以便临床灵活施用）。
补阴，凉血
味甘、苦，性寒，质地沉重，气味阴降。归手少阴心经、足少阴肾经、手厥阴心包经、足厥阴肝经，以及手太阳小肠经。滋养阴液，退除虚阳，生血并凉血。
治疗血虚发热（《内经》说：阴虚产生内热），劳损引起的咳嗽（咳嗽属阴虚者，地黄丸是主要药物，也能化痰。朱丹溪说：久病导致阴火上升，津液凝聚成痰而非生成血液，应当补血以制约相火，痰自然消除），痿证、痹证、惊悸（受刺激而心跳加速叫惊，没有外界刺激而心脏自动跳动叫悸，即怔忡。有的因心虚火动引起，有的因肝虚胆怯引起，有的因水饮停聚在心下引起，火畏惧水所以心悸。地黄能交通心肾并补益肝胆，也能利水，因此能治疗这些病症）。吐血、鼻衄、尿血（排尿疼痛为血淋，不痛为尿血。由心、肾气机郁结，或忧思过度、房劳所致，多属于虚寒证，不可单纯当作热证治疗）血晕、崩漏（《内经》说：阴虚而阳脉搏动剧烈称为崩），脚底发热疼痛，跌打骨折筋断（生地一斤，瓜姜糟一斤，生姜四两，炒熟后敷于受伤处，凉了便更换。另外，生地汁三分，酒一升半，煎煮后服用，可消除跌打损伤的瘀血），填补骨髓，促进肌肉生长，通利大小便，调理月经，安胎，又能杀虫。治疗心腹急痛（《海上方》记载：将地黄捣汁和面做成面食食用，能促使虫体排出，忌用盐。《本草汇》记载：朱丹溪说治气病要补血，虽然不一定对症，但也无害。却不知道血药属阴，性质凝滞，如果胃虚气弱的人，过量服用当归、地黄等药剂，反而会导致痞闷，饮食减少，变证百出，至死都不醒悟，岂不可惜！大抵血虚固然不能专门补气，而气虚也不能单纯补血。凡是劳损疾病，阳虚宜用四君子汤补气；阴虚宜用四物汤补血；阴阳俱虚者，宜合用，名为八珍汤）。
江浙产的地黄，南方阳气力量微弱；北方产的地黄，纯阴之力强大，以怀庆府出产、肥大且中心呈菊花心状的为佳。酒制则药力上行并向外发散，姜制则不腻膈。与贝母相反。畏芜荑。忌食莱菔（萝卜）、葱、蒜及铜铁器。与酒、麦冬、牡丹皮、当归配伍效果良好。
Greatly Clears Fire
Sweet and bitter in flavor, extremely cold in nature, entering the Heart and Kidney meridians. It clears Bing fire (Xiao Chang is Bing fire; the Heart and Xiao Chang are exterior-interior pairs; Daoyi San uses it together with Mutong), clears Dry Metal (referring to Stomach and Large Intestine fire), eliminates blood stasis, unblocks menstruation, and pacifies various rebellious flows of blood. It treats hematemesis (vomiting blood), epistaxis (nosebleed), and metrorrhagia (profuse uterine bleeding) (Sputum-blood: blood mixed with saliva; Hemoptysis: blood coughed up with phlegm, or streaks of blood, originating from the Kidney and Lung meridians. Blood vomiting upward from the hypochondrium belongs to the Liver meridian. Epistaxis: blood overflowing from the head/nose. Coughing blood: blood within sputum, belonging to the Lung meridian. Vomiting large quantities like basins or bowls belongs to the Stomach meridian. Continuous menstrual leakage is called Metrorrhagia; due to blood heat causing reckless flow, this herb cools the blood. Contraindicated for deficient persons; Gan Di Huang may be used instead). It treats Yang excess in Cold Damage (Shanghan), and high fever in smallpox/rash diseases (frequently used for rashes, though not recorded in ancient Materia Medica texts). Excessive use damages the Stomach.
Freshly dug Sheng Di Huang can be crushed and its juice drunk, or processed with wine to avoid damaging the Stomach. Raw form is cold; dried form is cool; cooked form is warm (thus divided into three categories for convenient application).
Nourishes Yin, Cools Blood
Sweet and bitter, cold in nature, heavy and descending. Enters the Hand-Shaoyin (Heart), Foot-Shaoyin (Kidney), Hand-Jueyin (Pericardium), Foot-Jueyin (Liver), and Hand-Taiyang (Small Intestine) meridians. Nourishes Yin, retreats Yang, generates blood, and cools blood.
It treats blood-deficiency fever (The Classic states: "Yin deficiency generates internal heat"), consumptive cough (For cough due to Yin deficiency, Dihuang Wan is a key medicine, also resolving phlegm. Zhu Danxi stated: "In chronic illness, Yin fire ascends, fluids condense into phlegm rather than generating blood; one should tonify blood to control Ministerial Fire, and phlegm will resolve itself"), atrophy syndrome (Wei Bi), bi-syndrome, palpitations, and fright (Fright is heart agitation triggered by external stimuli; Palpitation is spontaneous heart agitation without external trigger, also known as Zhengchong. Causes include Heart deficiency with fire movement, Liver deficiency with Gallbladder timidity, or water retention below the Heart where fire fears water. Dihuang communicates Heart and Kidney, benefits Liver and Gallbladder, and promotes water metabolism, thus treating these conditions). It treats hematemesis, epistaxis, and hematuria (Painful urination with blood is Xue Lin; painless is Hematuria. Caused by Qi stagnation in Heart/Kidney, worry, or sexual exhaustion; mostly deficiency-cold, not solely heat). It treats syncope due to blood loss and metrorrhagia (The Classic states: "Yin deficiency with vigorous Yang pulse constitutes Metrorrhagia"), burning pain in the soles of feet, fractures and severed tendons (One jin of Sheng Di Huang, one jin of melon-ginger lees, four liang of fresh ginger, stir-fried and applied cold to the injury site; alternatively, 3 fen of Sheng Di Huang juice with 1.5 sheng of wine, boiled and taken orally to resolve traumatic blood stasis). It fills the marrow, grows muscle, promotes bowel and bladder movements, regulates menstruation, calms the fetus, and kills parasites. It treats acute abdominal pain (Hai Shang Fang records: Crush juice, mix with flour to make food, expels parasites, avoid salt. Bencao Hui records: Zhu Danxi said treating Qi disease by tonifying blood is harmless even if not perfectly targeted. However, blood-tonifying herbs are Yin and cloying; excessive use in those with weak Stomach Qi causes fullness, reduced appetite, and myriad complications until death. Generally, blood deficiency requires blood tonification, not Qi; Qi deficiency requires Qi tonification, not just blood. For consumptive diseases: Yang deficiency suits Sijunzi Tang; Yin deficiency suits Siwu Tang; both suit Bazhen Tang).
Di Huang from Jiangsu/Zhejiang has weak Yang energy due to southern climate; Northern Di Huang has strong pure Yin energy. The best quality comes from Huaqing, characterized by plumpness and a chrysanthemum-heart center. Wine-processing directs action upward and outward; Ginger-processing prevents cloying the chest. It is incompatible with Fumu (Fritillaria). It fears Wuyi (Alchornea). Avoid Radish, Scallion, Garlic, and copper/iron vessels. Harmonizes well with Wine, Dongchong Xiacao (Ophiopogon), Mudanpi, and Danggui.