Always Suffering from Heat Symptoms, Toothaches, and Recurring Mouth Ulcers? Doctor Zhu Danxi’s Famous Theory “Yang in Excess, Yin Deficient” Is Really All About Kidney Essence (shen jing)
Patient search terms: recurring mouth ulcers / toothache / sore throat / upper-body heat / kidney essence deficiency (shen jing bu zu) / deficient fire flaring upward / yin deficiency with yang in excess
Corresponding medical concepts: yin deficiency with fire / kidney essence deficiency pattern · “shallow water cannot nourish the dragon” (water-deficiency with fire-flaring)
Opening: one sentence that got Zhu Danxi cursed at for hundreds of years
In the history of Chinese medicine, there is one sentence that stirred enormous controversy and brought hundreds of years of abuse down on the man who proposed it. That sentence is — “yang is in excess, yin is deficient” (yang you yu, yin bu zu).
💬 Note from Doctor Luo: In the Ming dynasty, Doctor Zhang Jingyue opposed this idea strongly, and later generations piled on. Even today many people keep repeating the old criticism: where is yang in excess? Yang is deficient too! Some doctors even say: “In all my patients with yin deficiency I couldn’t find a single one — they’re all yang deficient.” What is really going on in this debate? I have read Zhu Danxi’s original text over and over, and the more I read it, the clearer it becomes — what Zhu Danxi was saying is not at all what later generations understood. Today, let’s explain this essay thoroughly.
Starting with Ge Zhi Yu Lun: real theoretical debate in Chinese medicine began with him
Zhu Danxi wrote a book called Ge Zhi Yu Lun (Inquiries on the Fulfillment of Knowledge). “Ge zhi” refers to the Confucian discipline of ge wu zhi zhi — investigating things to extend one’s knowledge. The book is thin and short, but historically it matters enormously: with this book, Chinese medicine acquired its first true theoretical debates.
💬 Note from Doctor Luo: Why with him? Because earlier, Confucianism was an orthodox school — you learned whatever your teacher taught, with the classics as the basis. In the Song dynasty, the Cheng-Zhu school of Neo-Confucianism arose; Confucian scholars began debating theory and probing the reasoning behind the classics, and various schools of thought emerged. Zhu Danxi’s teacher Xu Qian was a direct disciple in Zhu Xi’s lineage, so by scholarly generation Zhu Danxi was also in Zhu Xi’s orthodox line; he studied Cheng-Zhu Neo-Confucianism with great diligence and inherited Zhu Xi’s style of arguing with people and debating theory. When he turned to medicine, he felt that some people’s readings of the Huang Di Nei Jing (Yellow Emperor’s Inner Canon) were wrong, so he began to dispute and write — besides Ge Zhi Yu Lun, he also wrote Ju Fang Fa Hui (Elucidations of the Formulary of the Bureau). After him, the various schools of Chinese medicine emerged.
How did the various schools come about? Each physician saw a blank spot in Chinese medical theory and stepped forward to fill it. For example, Doctor Li Dongyuan explained the spleen-stomach and qi-tonifying content of the Inner Canon superbly, leaning toward tonifying qi; Doctor Zhu Danxi, in contrast, leaned toward nourishing blood and yin, and was especially skilled with Si Wu Tang (Four Substances Decoction) plus blood-nourishing herbs.
💬 Note from Doctor Luo: See — Li Dongyuan tonifies qi, Zhu Danxi nourishes blood and yin; put the two together and you have both qi and blood covered. How should one study the various schools? Take their strengths, and stay fair-minded. The worst thing is to read one school, think it’s wonderful, and then stand in its corner cursing the others — that only means you haven’t reached a certain level yet, you’re still wandering around at the bottom. At the true high level, you hold all the schools in your mind, and take each one’s specialty into your heart. That is the superior way. In Chinese medicine, whoever takes the middle path among them is supreme.
What is yin? — far more than just “coolness”
So what exactly is the “yin” Zhu Danxi talks about? Yin is the body’s material foundation that governs stillness and moistening. What does it include?
First, blood. Zhu Danxi’s formulas are full of blood-nourishing herbs — after studying Zhu Danxi, you should know how to nourish and supplement blood; blood is part of yin.
Second, fluids (jin ye). All the liquid substances in the body. Zhu Danxi placed enormous importance on clearing heat, using herbs like huang lian (coptis) and huang bai (phellodendron) to clear it.
💬 Note from Doctor Luo: Some people say bitter-cold herbs damage yang! Listen — when there is genuine pathogenic heat in the body, you truly must use them. Many of Zhang Zhongjing’s formulas “urgently purge to preserve yin” — the Cheng Qi Tang (Order the Qi Decoction) family is full of cold herbs. Why? Because as long as pathogenic heat sits in the intestines, it will quickly dry up the body’s fluids; once the fluids are exhausted, the illness turns critical fast. So you promptly move the bowels and clear the heat — what you are protecting is the fluids: as long as the fluids remain, the body can recover. Treating heat diseases today, like COVID-19, also requires cool herbs such as shi gao (gypsum) to preserve the fluids — otherwise you truly cannot control a heat condition. Zhu Danxi inherited this line of thinking from Zhang Zhongjing, and it is correct.
Third, essence (jing). This is the most core and most easily overlooked element in Zhu Danxi’s “yin deficiency.”
Essence: the core the ancients “hid” inside yin
What is essence? Prenatal essence (xian tian zhi jing) is the genetic material you inherited from your parents; postnatal essence (hou tian zhi jing) is formed when the clear qi you breathe and the refined nutrients of the food you eat combine with the essence of the five viscera. Postnatal essence combines with prenatal essence to become each person’s kidney essence, sealed and stored in the kidneys — this is Chinese medical theory, and everyone should remember it.
💬 Note from Doctor Luo: Essence is the core of the human body — you need genetic material to grow at all. Essence can transform into qi, giving rise to the two qi of yin and yang: kidney essence produces kidney yin and kidney yang, which is how the body comes to have yin and yang, matter and function. Essence leans toward the material foundation, so the ancients always linked essence with yin; in the broad sense essence also belongs to yin — but that linkage caused confusion: sometimes when they said “yin” they meant essence, sometimes when they said “essence” they meant yin, and later generations lost track of essence’s true status. I have always argued that essence should be set apart on its own — it sits between yin and yang, containing the sprouts of both; the moment it transforms into qi, it generates the two qi of yin and yang. Once you get this position clear, going back to Zhu Danxi’s essay makes everything click.
When essence is depleted, fire rushes upward — “shallow water can no longer nourish the dragon”
What happens when essence is depleted? Either yin suffers or yang suffers, depending on the bias of your constitution. Either way, your vitality falters: you age quickly, children stop growing, and the whole life function of the body declines. If the bias is toward yin deficiency —
💬 Note from Doctor Luo: This is what we call “shallow water can no longer nourish the dragon” — when kidney water runs low, deficient fire gallops upward, and the upper body shows all kinds of heat symptoms while below… upper heat with lower cold: the lower body is icy, the lower back is sore and weak, and above you get toothaches, sudden mouth ulcers, sore swollen throats, trigeminal neuralgia, eye problems… all sorts of strange complaints. Especially after the winter solstice each year, as spring gradually approaches, such patients are particularly numerous.
Just a couple of days ago, a neighbor from Doctor Luo’s hometown came to ask him: my eye suddenly hurt all night, the pain is unbearable — what should I do?
💬 Note from Doctor Luo: I said, send me a photo of your tongue — one look, kidney essence deficiency. He said he’d had recurrent styes (chalazia) for years. I said your deficient fire keeps running up top; use Yin Fire Guide Decoction (Yin Huo Tang), with a large dose of shu di huang (prepared rehmannia) — 60 g of shu di huang to replenish his kidney essence. After one dose he told me: the eye pain had eased markedly, the effect was excellent — the deficient fire had come down. This kind of case is everywhere; I have seen far too many upper-body deficient-heat conditions caused by kidney essence deficiency.
How does kidney essence get depleted? — it is consumed away
Kidney essence deficiency is usually not congenital — it is consumed: staying up late, overthinking, excessive desire… modern people consume far, far too much.
💬 Note from Doctor Luo: Once kidney essence is deficient, a person enters a deficient-heat state — some are even clearly yang deficient with insufficient kidney yang, yet still have deficient fire up above. In such cases, if you use a large dose of shu di huang to replenish kidney essence, you must pair it with a little rou gui (cinnamon bark) — without it the fire will not come down; you have to warm the yang a bit and guide the fire back to its origin. If the yang deficiency is obvious, add kidney-warming, yang-tonifying herbs like ba ji tian (Morinda root). So you see, whenever kidney essence is on the verge of depletion, dryness-heat symptoms immediately appear in the upper body — kidney essence deficiency is the root of the person.
Opening the first essay of Ge Zhi Yu Lun: what was Zhu Danxi actually writing about?
In his essay, Zhu Danxi begins with the yin and yang of heaven and earth, the sun and the moon — the kind of cosmology the ancients always brought up; treat it as an analogy. What really matters comes later.
💬 Note from Doctor Luo: He says, yin qi is hard to build up — yin qi is especially difficult to mature, which is why the ancients waited until their late twenties or thirties (men married at thirty, women at twenty) before marriage — they feared consuming yin qi too early. The Inner Canon says “at age forty, yin qi is naturally halved” — past forty your yin qi is already half gone, and your body begins its decline. It also says “men’s essence is exhausted at sixty-four, women’s menses cease at forty-nine” — the yin qi you manage to build up only supports about thirty years of seeing, hearing, speaking and moving before it is already deficient. Then Zhu Danxi says the famous line: “Human desire is boundless — how can this hard-to-form, easy-to-lose yin qi ever supply it?” Human desire has no end; this little bit of yin qi that is so hard to build and so easy to lose — how can it withstand your kind of consumption?
Notice — on the surface he says “yin qi” throughout, but read on and it becomes clear: what he is really talking about is essence, kidney essence.
“The heart is the monarch fire; stirred by things it moves easily” — even a glance drains your essence
Zhu Danxi continues: “The heart is the monarch fire; stirred by things it moves easily.” The heart, stirred by “things,” moves easily. What are these “things”?
💬 Note from Doctor Luo: He writes too obscurely, so let me tell you plainly — the “things” are members of the opposite sex. When you see a beautiful woman, your heart gives a little jump — the heart moves, the minister fire moves with it, and the qi and blood in your body start turning; in modern terms, hormone secretion begins to change. “When it moves, essence secretly walks away”: even though you have no sex life, the minister fire flares up, and essence is secretly draining away and being consumed. That is why the sages simply told people to collect the heart and nourish the mind — “the ancients, by not seeing what they desired, kept their hearts from being disturbed,” a thought from the Dao De Jing: don’t put yourself in that environment; what the eye does not see, the heart will not be stirred by.
Some people say: come on — I just admire a pretty face, how does that consume kidney essence? Doctor Luo offers an analogy —
💬 Note from Doctor Luo: Imagine two armies at war. Your side keeps receiving false intelligence — “the enemy is attacking!” The whole army jumps into the trenches, loads their rifles, gets ready… nothing happens, they withdraw. Suddenly the alarm sounds again, back to the trenches, load rifles again… Ten false alarms a day. After a month, what’s the combat effectiveness of that army? Every mobilization consumes materiel! Emperor Taizong of Tang (Li Shimin) was a master of this in war — feint one way, exhaust the enemy until they are weary, then strike, and win every time. The body’s essence is the same: you see a beautiful woman, your heart races, hormones secrete, your blood circulation says “how lovely!” — do you think the body consumes nothing? So Zhu Danxi was absolutely right: looking at beautiful women stirs the minister fire and drains kidney essence — this is the truth that only a true scholar sees clearly.
When is essence most easily damaged? — Zhu Danxi’s four layers of taboo
In this essay, Zhu Danxi lists the times when essence is most vulnerable, layer by layer. Doctor Luo summarizes them into four layers of taboo:
Layer one: the yearly void. In the lunar months of the fourth, fifth, sixth, tenth, and eleventh, the yin qi is at a disadvantage and easily damaged — the Inner Canon says “if you fail to store essence in winter, you will certainly suffer warm disease in spring.” During these months you should restrain desire and protect essence as much as possible; the ancients, “when at leisure, slept alone,” keeping away from the opposite sex.
Layer two: the monthly void. Around the first quarter moon, last quarter moon, and the empty moon (new moon) each month also count as a monthly void — best to avoid sexual activity then as well.
Layer three: the daily void. Strong wind, heavy fog, thunder and storms, sudden cold or heat, solar and lunar eclipses, and great emotional upheaval — worry, anger, fright, grief — plus being drunk, overeating, extreme fatigue, or spending every day scheming about promotions and official rank — none of these times are suitable for intercourse.
Layer four: during illness. Just recovered from a major illness, or with sores/boils actively on the body — this layer exceeds even the daily void; it can happen at any time, and this is when you must be most careful not to damage kidney essence.
💬 Note from Doctor Luo: Once kidney essence is damaged, Zhu Danxi says, all kinds of diseases arrive — heat conditions especially, and people age frighteningly fast, showing an old man’s bearing while still in their prime. According to his reckoning, most of the year is unsuitable for indulgence — these are the old rules the ancients used to protect their essence, and every word is written for your health.
Even an iron man’s heart would move — Zhu Danxi wrote so bluntly that later generations blushed
There is a passage in Zhu Danxi’s original text that Doctor Luo says he finds delightful every time he reads it:
💬 Note from Doctor Luo: “With softness and warmth pressing against your body, sweet voices filling your ears, painted faces and fragrant scents meeting your eyes and nose — who, even an iron man, could keep his heart unmoved?” A beautiful woman’s soft body pressed against your skin, lovely voices at your ear, a made-up face and the fragrance of rouge and perfume rushing at you — you’re an iron man, can your heart stay still? Some people nowadays try to explain this passage away, claiming “fragrance” means the smell of food and “colors” just means pretty colors — don’t twist it. Zhu Danxi said it clearly: this is about sex, plain and simple.
And most of what Zhu Danxi says here is addressed to men — because the problem really is more pronounced in men; women don’t have as strong a drive in this regard.
💬 Note from Doctor Luo: That’s why you’ll notice women on average live much longer than men. In the nursing homes I visit, it’s almost always the grandmother pushing the grandfather’s wheelchair — the husband usually goes first. There are many reasons; by Zhu Danxi’s theory, one of them is the consumption of kidney essence: women have all kinds of self-repair abilities, and they consume less kidney essence; men consume far too much — always stirred, always draining. A friend told me he glanced twice at a video of a woman dancing on Douyin (TikTok), and afterwards his feed was nothing but that kind of content — wall-to-wall swaying long legs. He posted about this online, and every male commenter said “my feed is exactly the same.” Ask any woman: is her feed full of muscular young men dancing? Basically not. Women’s feeds are scenery, travel — that difference is precisely the difference in kidney essence consumption between men and women.
Conclusion: understand kidney essence, and you finally understand Zhu Danxi
The first essay of Ge Zhi Yu Lun is titled “yang in excess, yin deficient,” and the whole essay is really about one thing: the importance of kidney essence.
💬 Note from Doctor Luo: In practice he excelled at nourishing blood and clearing heat to preserve fluids, but his most important theory was preserving kidney essence — sex is fine, but don’t let the minister fire flare recklessly, don’t keep your mind on it all the time. The sages teach you to collect the heart and nourish the mind, to read the classics, to reduce desire to the minimum, and to preserve kidney essence. Later generations misread him, imagining Zhu Danxi advocated damaging yang, clearing heat, and eliminating yang — so they attacked him as one-sided. In fact, they simply failed to understand the importance of kidney essence. Spend enough time in clinical practice, see enough patients, and you will know: a great many conditions are tied to kidney essence deficiency. Truly essence-sufficient people are rare; those who protect it well are healthy and long-lived, while those who don’t are plagued by a hundred diseases that are very hard to treat. The earlier kidney essence is depleted, the harder everything becomes to fix afterward.
As a scholar of Cheng-Zhu Neo-Confucianism, opening his very first essay with such a sensitive topic, using blunt language without apology — this is Zhu Danxi’s compassionate heart: he wanted everyone to be healthy. He closes the essay: “Treasure yourselves, and preserve the heavenly harmony within you” — may you all take care of yourselves and protect the life heaven has given you.
💬 Note from Doctor Luo: Friends, understand this essay and you understand Zhu Danxi’s intention. Tomorrow we’ll continue with Zhu Danxi’s theories — there are still many case studies waiting for us. Once you’ve studied them, you’ll never misunderstand him again. Alright, thank you friends, let’s stop here today — see you tomorrow.
What to take away
- “Yang in excess, yin deficient” was misunderstood for centuries. Zhu Danxi’s famous opening essay of Ge Zhi Yu Lun is not an attack on yang — read the whole text and it becomes clear he was really writing about kidney essence (shen jing) and its protection.
- Yin means blood, fluids (jin ye), and essence. Zhu Danxi’s nourishing-blood formulas and his clearing of heat both serve one goal: protect the body’s fluids, just as Zhang Zhongjing’s “urgent purgation to preserve yin” does.
- Essence is the root that generates yin and yang. Prenatal essence plus postnatal essence, sealed in the kidneys, transforms into kidney yin and kidney yang. Deplete it and you age fast, children stop growing, and the whole body declines.
- “Shallow water cannot nourish the dragon.” When kidney essence runs low, deficient fire flares upward: toothache, sudden mouth ulcers, sore throat, trigeminal neuralgia, eye trouble — with an icy lower body and weak sore back. The classic answer is a large dose of shu di huang (prepared rehmannia) with a little rou gui (cinnamon bark) to guide the fire home.
- Essence is consumed, not lost by accident. Staying up late, overthinking, and unchecked desire all drain it — by Zhu Danxi’s teaching, even looking at beautiful women stirs the minister fire and secretly consumes essence.
- Four layers of taboo: yearly, monthly, daily, and during illness. Lunar months four, five, six, ten and eleven; the quarter moons and new moon; storms, eclipses, great emotion, drunkenness, overeating, exhaustion; and any illness. Restrain desire, collect the heart, and preserve essence — that is the way to longevity.
Compiled from Doctor Luo Dalun’s lecture series on Zhu Danxi.