下血脉浮弱，按之绝者，下血。因荣卫之气妄行，在春夏为溢上，在秋冬为
泄下，左脉洪大伏毒下血；脉虚而数，毒者暑也。
内热下血，关后沉数。
肺受风热，传下大肠，名肠风。
先因便结而后下血，右尺脉浮，食毒物积于肠中，血随粪下，遇食则发，名
藏毒下血，脉见积脉。
四物汤 升麻 秦艽 阿胶 白芷
热加黄连（酒煮温散） 栀子（炒）
虚加干姜（炮） 五倍子
如寒药用加辛升温散，一行一止。
胃风汤 治风毒客肠胃，动则下血。
四物去地黄，加人参、白术、桂枝、茯苓等分。
凉血地黄汤 治肠 下血，水谷与血另作一派。
知母（炒） 黄柏（一钱炒） 熟地 川归（各五分） 槐子（炒） 青皮（各五钱）
越桃散 治下血与血利。
栀子仁 槐花 枣 干姜
上各烧存性，米饮下三钱。
伏龙肝散 治便血因内外有感，停凝在胃，随气下通妄行。
伏龙肝（一两） 白术 阿胶 黄芩 地黄 甘草（三钱）
阴结 夫邪入五脏则阴脉不和，血留之渗入肠间，脉虚涩也。
生地黄汁 小蓟汁（各一斤） 砂糖熬膏 地榆 阿胶 侧柏叶 赤小豆（五两浸芽出日干）
川归（一两） 为末下。
治先血后便，谓之近血，水下前末。
治下血 五灵脂（炒）末芎归汤下。
下血证见脉象浮而弱，重按则感觉中断或消失的，属于下血。这是由于营卫之气妄行所致：在春夏季节表现为血液上溢，在秋冬季节表现为血液下泄；若左脉洪大，提示有伏毒导致下血；若脉象虚而数，提示病因为暑毒。
先因大便干结而后出现便血，右尺脉浮，是因食用有毒食物积滞于肠道，血液随粪便排出，遇到特定食物则发作，称为藏毒下血，脉象表现为积脉。
方药：四物汤、升麻、秦艽、阿胶、白芷。
若有热象，加黄连（用酒煮以温散）、栀子（炒）。
若属虚证，加干姜（炮制）、五倍子。
如果使用寒性药物，需加入辛温之品以温散，使药力一行一止，相互制约。
胃风汤：治疗风毒客居于肠胃，触动后导致下血。
组成：四物汤去掉地黄，加入人参、白术、桂枝、茯苓，各等分。
凉血地黄汤：治疗肠道下血，水谷与血液分开排泄。
组成：知母（炒）、黄柏（一钱，炒）、熟地黄、川当归（各五分）、槐子（炒）、青皮（各五钱）。
越桃散：治疗下血及血痢。
组成：栀子仁、槐花、枣、干姜。
以上药材均烧存性，用米饮送服三钱。
伏龙肝散：治疗便血因内外感邪，停滞凝涩于胃，随气机下行而妄行。
组成：伏龙肝（一两）、白术、阿胶、黄芩、地黄、甘草（三钱）。
阴结：邪气侵入五脏，导致阴脉不和，血液留滞渗入肠间，脉象虚涩。
方药：生地黄汁、小蓟汁（各一斤），砂糖熬成膏，地榆、阿胶、侧柏叶、赤小豆（五两，浸泡发芽后晒干）、川当归（一两）。
研为末服用。
治疗先出血后大便的情况，称为近血，用水送服上述粉末。
Lower rectal bleeding with a floating and weak pulse, which feels interrupted or disappears upon deep pressure, indicates lower rectal bleeding. This is caused by the reckless movement of Ying (Nutritive) and Wei (Defensive) Qi: in spring and summer, it manifests as upper overflow; in autumn and winter, it manifests as lower leakage. A large left pulse suggests hidden toxicity causing lower rectal bleeding; a deficient and rapid pulse suggests heat-toxin from summerheat.
Lower rectal bleeding due to internal heat presents with a deep and rapid pulse at the Chi position posteriorly.
When the Lung is affected by wind-heat, and the pathogen transmits to the Large Intestine, it is called Chang Feng (Intestinal Wind).
If constipation precedes the bleeding, and the Right Chi pulse is floating, it is due to food toxins accumulating in the intestines, with blood following the stool downward. It occurs upon exposure to certain foods and is called Zang Du Lower Rectal Bleeding (Visceral Toxin Lower Rectal Bleeding), presenting with an accumulation pulse.
Formula: Si Wu Tang (Four Substances Decoction), Sheng Ma (Cimicifugae Rhizoma), Qin Jiao (Gentianae Macrophyllae Radix), E Jiao (Colla Corii Asini), Bai Zhi (Angelicae Dahuricae Radix).
For heat, add Huang Lian (Coptidis Rhizoma) (decocted with wine for warm dispersion) and Zhi Zi (Gardeniae Fructus) (stir-fried).
For deficiency, add Gan Jiang (Zingiberis Rhizoma) (processed) and Wu Bei Zi (Galla Chinensis).
If cold-natured herbs are used, acrid-warm herbs should be added for warm dispersion, allowing the medicinal action to move and rest alternately.
Wei Feng Tang (Stomach Wind Decoction): Treats wind-toxin lodging in the stomach and intestines, triggering lower rectal bleeding upon movement.
Composition: Si Wu Tang (Four Substances Decoction) without Di Huang (Rehmanniae Radix), plus Ren Shen (Ginseng Radix), Bai Zhu (Atractylodis Macrocephalae Rhizoma), Gui Zhi (Cinnamomi Ramulus), and Fu Ling (Poria), in equal proportions.
Liang Xue Di Huang Tang (Cool Blood and Rehmannia Decoction): Treats intestinal lower rectal bleeding where water/grain and blood are excreted separately.
Composition: Zhi Mu (Anemarrhenae Rhizoma) (stir-fried), Huang Bo (Phellodendri Cortex) (1 qian, stir-fried), Shu Di Huang (Prepared Rehmanniae Radix), Chuan Gui (Angelicae Sinensis Radix) (each 5 fen), Huai Zi (Sophorae Japonicae Flos) (stir-fried), Qing Pi (Citri Reticulatae Pericarpium Viride) (each 5 qian).
Yue Tao San (Prunus Persica Powder): Treats lower rectal bleeding and bloody dysentery.
Composition: Zhi Zi Ren (Gardeniae Semen), Huai Hua (Sophorae Japonicae Flos), Zao (Jujubae Fructus), Gan Jiang (Zingiberis Rhizoma).
All ingredients are charred but retain their nature (burned to preserve efficacy), taken with rice drink, 3 qian per dose.
Fu Long Gan San (Dragon's House Earth Powder): Treats hematochezia caused by external and internal pathogens stagnating and coagulating in the Stomach, flowing downward with Qi and bleeding recklessly.
Composition: Fu Long Gan (Hearth Earth) (1 liang), Bai Zhu (Atractylodis Macrocephalae Rhizoma), E Jiao (Colla Corii Asini), Huang Qin (Scutellariae Radix), Di Huang (Rehmanniae Radix), Gan Cao (Glycyrrhizae Radix et Rhizoma) (3 qian).
Yin Jie (Yin Knotting): When pathogens enter the Five Zang organs, Yin pulses become disharmonious, blood stagnates and seeps into the intestines, resulting in a deficient and choppy pulse.
Prescription: Sheng Di Huang Zhi (Juice of Raw Rehmanniae Radix), Xiao Ji Zhi (Juice of Cirsii Herba) (each 1 jin), refined sugar paste, Di Yu (Sanguisorbae Radix), E Jiao (Colla Corii Asini), Ce Bai Ye (Biota Tops), Chi Xiao Dou (Adzuki Bean) (5 liang, soaked until sprouted then dried), Chuan Gui (Angelicae Sinensis Radix) (1 liang).
Grind into powder and take.
For bleeding preceding stool, termed Jin Xue (Near Bleeding), administer the above powder with water.
For treating lower rectal bleeding: Wu Ling Zhi (Trogopterori Faeces) (stir-fried) ground into powder, taken with Xiong Gui Tang (Ligusticum and Angelica Decoction).