猪苓，味苦、甘、淡，气平。降也，阳也，无毒。入肾与膀胱经。通淋消肿满，除湿利
小便
泄滞，助阳利窍，功专于行水，凡水湿在肠胃、膀胱、肢体、皮肤者，必须猪苓以利之。然
而水湿之症有阳、有阴、有虚、有实，未可一概利之也。倘阴虚之症，轻用猪苓以泻其水，
水去阴亦消亡，必有口干舌燥之症。况原无水湿之症，利之则重亡津液，阴愈虚矣。甚则有
利小便，欲行点滴而不可得者，非误利之明验乎。虽然水湿之邪既在人身，岂可以阴虚难治
，竟置于不治哉？用猪苓利水之药，仍入之阴药中，阴既不虚，而湿亦自利，安在猪苓之不
可用乎。
或问猪苓利水，胡为利水而水不通，且多急闷而不可解，何也？此火蓄膀胱，而上焦之
气不
升，肺金清肃之令不行于下焦之故也。夫膀胱泻水也，然必得肺金之气清肃下行，而乃水走
于阴器而出。猪苓但利水，而不能升上焦之气，上焦有火，过抑肺金，清肃之令不能行于下
焦，不用降火之品，而唯从事于利水。所以，用猪苓而不效，非猪苓之不能利水也。
或问猪苓导水，使火邪从小便而出，是引火邪之下出也，然仲景张公往往用猪苓汤以散
邪，何也？盖猪苓之性，不特下走于阴窍，而且兼走于皮毛之窍，仲景夫子用猪苓汤者，恶
邪不走膀胱而走皮肤，虑亡阳之症，所以用之，即引火邪从皮毛而外出也。然则猪苓不特引
水下泄，而亦能引火外泻也。
或问猪苓利水，何能解口之不渴也？夫小便数而口不渴者，火蓄于膀胱也。火蓄则熬干
其水
，水沸而为热，所以作渴。用猪苓以利水，实所以泻火，火泻而水独存，则津液通，而上润
于口舌之间矣。然则猪苓非利水之药，乃生津之药也。
或疑猪苓为生津之药，终不可为训。曰∶猪苓利水尽，则口益干，而欲其口舌之生津，
难矣
。所谓生津者，止能生于多水之症，而不能生于无水之症。无水之症，泻水则水涸而火起；
多
水之症，泻水则火降而水升。水既升矣，而津液有不润于口齿者乎。是猪苓之生津，生于利
水以去火，而非概生于利水也。
或疑猪苓、泽泻，同是利水之物，而吾子偏分出功用之不同，非好奇耶？曰∶猪苓、泽
泻用
既不同，义自各别，有异言异，有同言同，何好奇之有。
猪苓，味道苦、甘、淡，性质平和。其气主降，属阳，无毒。归入肾经与膀胱经。能通利小便以消除淋证，消肿满，祛除体内湿气并通利小便，疏导停滞之气，辅助阳气通畅窍道，功效专门在于行水。凡是水湿邪气停留在肠胃、膀胱、肢体、皮肤部位的，必须用猪苓来利水祛湿。然而，水湿病症有阳证、阴证、虚证、实证之分，不能一概而论地单纯使用利水法。如果是阴虚的病症，轻率地使用猪苓来泻水，水液去除了，阴气也随之消亡，必然会出现口干舌燥的症状。况且原本就没有水湿病症，如果强行利水，则会严重耗伤津液，使阴虚更加严重。甚至有因为误用利水药，导致想排尿却点滴不得的情况，这难道不是误用利水法的明显证据吗？虽然水湿邪气既然存在于人体，难道因为阴虚难治，就完全放弃治疗吗？在使用猪苓这类利水药时，应当将其配伍在滋阴药物中，这样阴气既不会亏损，湿气也能自然被利去，哪里还说猪苓不可用呢？
有人问：猪苓利水，为什么有时利水后水反而不通，并且出现多急闷而不可缓解的情况，这是为什么呢？这是因为火邪蓄积在膀胱，导致上焦之气不能上升，肺金清肃下降的功能不能下达于下焦的缘故。膀胱负责排泄水液，但必须依赖肺金之气清肃下行，水液才能流向阴器排出。猪苓只能利水，而不能提升上焦之气，如果上焦有火，过度抑制肺金，导致清肃之令不能行于下焦，此时如果不使用降火的药物，而只专注于利水，所以，使用猪苓而不见效，并不是猪苓不能利水，而是辨证用药不当所致。
有人问：猪苓引导水液，使火邪从小便排出，这是引火邪向下排出，但是张仲景先生往往使用猪苓汤来解散邪气，为什么呢？大概猪苓的药性，不仅向下走向阴窍，而且兼走皮毛的腠理孔窍。张仲景夫子使用猪苓汤，是担心邪气不走膀胱而走皮肤，顾虑亡阳的病症，所以使用它，即引导火邪从皮毛向外发散排出。既然如此，猪苓不仅能引导水液向下泄出，也能引导火邪向外泻出。
有人问：猪苓利水，怎么能解释口不渴的症状呢？小便利数而口不渴的，是因为火邪蓄积在膀胱。火邪蓄积会煎熬水液，水沸腾而产生热，所以造成口渴。使用猪苓来利水，实际上是为了泻火，火邪泻去而水液独存，那么津液就能通畅，向上滋润口舌之间了。既然如此，猪苓不仅仅是利水的药，更是生津的药。
有人怀疑猪苓作为生津的药，终究不能作为准则。回答说：如果猪苓将水利尽，那么口会更加干燥，想要它生津，就很难了。所谓生津，只能在水湿多的病症中生津，而不能在水湿少的病症中生津。无水（津亏）的病症，泻水则水枯竭而火更起；多水（湿盛）的病症，泻水则火降而水升。水既已上升，那么津液有不滋润口齿的吗？这就是猪苓的生津作用，产生于通过利水来去除火邪，而不是泛指所有利水都能生津。
有人怀疑猪苓和泽泻，同样是利水的药物，而你特别区分出它们功用的不同，这不是好奇吗？回答说：猪苓和泽泻的使用方法和原理自然各有区别，有的方面不同就说不同，有的方面相同就说相同，有什么好奇的呢。
Zhu Ling (Polyporus), with bitter, sweet, and bland flavors, has a neutral nature. It descends and belongs to Yang; it is non-toxic. It enters the Kidney Meridian and the Bladder Meridian. It promotes urination to alleviate strangury, reduces swelling and fullness, removes dampness, facilitates urination, unblocks stagnation, assists Yang in opening orifices, and its efficacy is specifically dedicated to promoting water metabolism. Whenever water-dampness pathogens reside in the intestines, stomach, bladder, limbs, or skin, Zhu Ling must be used to promote urination and drain dampness. However, water-dampness syndromes vary into Yang, Yin, Deficiency, and Excess types; one cannot indiscriminately apply diuretic methods. If a Yin-deficiency syndrome occurs, using Zhu Ling lightly to drain water will cause the loss of Yin along with the water, inevitably leading to symptoms such as dry mouth and tongue. Moreover, if there is no original water-dampness pathology, forcing diuresis will severely deplete body fluids, exacerbating Yin deficiency. In severe cases, patients may find themselves unable to pass even a few drops of urine despite the urge, which is clear evidence of misusing diuretics. Although water-dampness pathogens exist in the body, should treatment be abandoned simply because Yin deficiency is difficult to treat? When using Zhu Ling, a water-draining herb, it should be combined with Yin-nourishing herbs. This way, Yin remains intact, and dampness is naturally drained. Thus, Zhu Ling can indeed be used.
One might ask: Why does Zhu Ling sometimes fail to promote urination effectively, resulting in urinary retention accompanied by urgent oppression that cannot be relieved? This is due to Fire accumulation in the Bladder, preventing the Qi of the Upper Jiao from ascending, and causing the Lung Metal's descending and purifying function to fail in reaching the Lower Jiao. The Bladder excretes water, but this requires the Lung Metal's Qi to descend purely and heavily for water to flow out through the genitalia. Zhu Ling only drains water but cannot raise the Qi of the Upper Jiao. If Fire exists in the Upper Jiao, it excessively suppresses Lung Metal, preventing its purifying function from reaching the Lower Jiao. If one does not use herbs to descend Fire but focuses solely on draining water, Zhu Ling will prove ineffective. This inefficacy is not due to Zhu Ling's inability to drain water, but rather improper differentiation and treatment.
One might ask: Zhu Ling guides water, allowing Fire pathogens to exit via urination, which is guiding Fire downward. However, Master Zhang Zhongjing often uses Zhu Ling Tang (Polyporus Decoction) to disperse pathogens. Why? The nature of Zhu Ling not only travels downward to the yin orifices but also extends to the pores of the skin. Master Zhang Zhongjing uses Zhu Ling Tang because he fears pathogens moving from the Bladder to the skin, worrying about Yang collapse syndromes. Therefore, he uses it to guide Fire pathogens outward through the skin. Thus, Zhu Ling not only guides water downward for excretion but also guides Fire outward for discharge.
One might ask: How does Zhu Ling's diuretic action explain the symptom of "no thirst"? Frequent urination without thirst indicates Fire accumulation in the Bladder. Accumulated Fire boils the water, creating heat, which causes thirst. Using Zhu Ling to drain water is essentially to purge Fire. Once Fire is purged, water remains, allowing body fluids to circulate freely and moisten the mouth and tongue. Thus, Zhu Ling is not merely a diuretic but also a fluid-generating herb.
Some doubt whether Zhu Ling can truly generate fluids, considering it inappropriate as a standard principle. I reply: If Zhu Ling drains all water, the mouth becomes drier, making fluid generation difficult. The term "generating fluids" applies only to conditions with excessive water (dampness), not to conditions lacking water (fluid depletion). In fluid-depletion conditions, draining water leads to exhaustion of water and rising Fire; in dampness-excess conditions, draining water lowers Fire and raises Water. Once Water rises, body fluids naturally moisten the teeth and mouth. Therefore, Zhu Ling generates fluids by draining water to remove Fire, not by indiscriminate diuresis.
Some question why I distinguish the functions of Zhu Ling and Ze Xie (Alisma Rhizome), given both are diuretics, suggesting curiosity for its own sake. I answer: Zhu Ling and Ze Xie have different applications and principles. Differences should be stated as differences, similarities as similarities. There is nothing curious about this distinction.