The Body Clock 子午流注

The schedule

Classical medicine divided the day into twelve two-hour watches and gave each to a channel: qi was said to crest in the lung from 3–5 a.m., large intestine 5–7, stomach 7–9, spleen 9–11, heart 11–1, small intestine 1–3, bladder 3–5 p.m., kidney 5–7, pericardium 7–9, triple burner 9–11, gallbladder 11–1 a.m., and liver 1–3 a.m. — then back to the lung as the cycle turns^[1]. The name, "midnight-noon ebb and flow," says what it is: a tide chart for the meridians.

How it gets used

Mostly as an interpretive lens. Regular 1–3 a.m. waking reads as a liver matter — often the stress-constraint picture that pages like Xiao Yao San address; the pre-dawn cough that strikes at 4 points to the lung watch; the tradition's advice to breakfast well lands squarely in the stomach's 7–9 a.m. crest^[1]. Some acupuncturists time treatments to the schedule; most use it as the kind of pattern-hint that starts a conversation.

An honest comparison

Modern chronobiology agrees enthusiastically that the body runs on clocks — cortisol's dawn surge, liver metabolism's nightly rhythms, timed drug dosing — but its clocks were mapped by molecule, not by watch-of-the-channel, and the two systems' details don't line up into confirmation. Fair reading: the tradition noticed, a thousand years early, that when a symptom happens is data. That insight survives whatever becomes of the timetable.

Where to next

The clock is the meridian map set spinning. For the framework beneath both, start at what is qi?.

Reviewed 2026-08-25