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Shang Han Lun for Beginners: The Handbook Behind the Formulas

Around the year 200, an epidemic swept through the clan of a Chinese physician named Zhang Zhongjing. In his preface he writes that of two hundred relatives, two-thirds died within a decade — most of them from “cold damage.” His answer was a book: the Shang Han Lun, the Treatise on Cold Damage. Eighteen centuries later it is still in print, still memorized by students, and still the source of formulas prescribed every day. This page is the short introduction. The free tool at the bottom is where the book becomes something you can touch.

Not a theory book — a field manual

Most famous medical classics explain the universe. This one behaves like a senior doctor’s notebook from a disaster zone: terse, practical, organized by what you are looking at rather than by what things mean. Each entry names a pattern — this cluster of signs, at this stage — and gives the formula for it, the dose, the decoction method, and the warnings. Theory exists, but it is kept in its place: underneath the cases, holding them up.

The six stages, in one breath each

Zhang’s organizing idea is that illness moves. An externally contracted disease walks through six stages (“conformations”), and the formula depends on which room it is currently in:

• Taiyang 太阳 — the surface. The illness is at the gates: chills, fever, stiff neck, a floating pulse. Open the surface and show it out.
• Yangming 阳明 — the furnace. It has gone inside and turned to heat: high fever, sweat, thirst, a body like a stove. Clear the heat, protect the fluids.
• Shaoyang 少阳 — the hinge. Half in, half out: alternating chills and fever, bitter taste, a stuck feeling. Don’t push either way — harmonize the hinge.
• Taiyin 太阴 — the cold kitchen. Now the illness is cold and the digestion is failing: fullness, vomiting, no thirst. Warm the center.
• Shaoyin 少阴 — the deep reserves. The body’s fire itself is low — or heat is burning in the depths. The most delicate room in the house.
• Jueyin 厥阴 — the last hinge. Hot and cold tangled together at the end of the line. The book’s hardest patterns, and its most famous formulas.

One cold, one formula — use the wrong one, and the illness doesn’t just stay. It gets worse, and moves deeper.

That sentence is the book’s beating heart, and the reason stage matters more than disease name. A “cold” in the Taiyang room gets Guizhi Tang; the same “cold” driven into Yangming by a wrong prescription is a different emergency with a different formula. Modern textbooks of Chinese medicine are largely commentaries on this architecture — the Shang Han Lun is the building itself.

Try it: the free formula finder

Reading about pattern-matching is one thing; watching it work is another. Below is the free edition of the Shang Han Lun formula tool built from this book — the same tool our Chinese sister site runs. Work in the two opening stages, Taiyang and Yangming: pick the signs, and the tool walks you to the classical formula, with the original text.

How to read the tool (its interface is the original Chinese — treat the characters as part of the exhibit):

• 六经辨证 — “pattern mode”: start from a stage （太阳 = Taiyang, 阳明 = Yangming) and narrow down by signs.
• 按症状查 — “by symptom”: start from what you feel and let it route you.
• 方剂 means “formula.” Locked rooms belong to the full edition — all six stages, 57 formulas — which lives at rootbro.com.

One honest warning, in the spirit of the book itself: the tool teaches how the classical system reasons. It is a study instrument, not a prescription machine — the formulas in it are medicines, and the man who wrote them down was a physician treating patients in front of him, not readers alone with a screen.

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