Background
In TCM, qì xū describes a state where the body's functional energy is running low. The formulas grouped under this tag share a common thread: they address situations where "something that should be moving isn't moving enough" — whether that's the defensive qi that should be keeping the pores closed, the middle-burner qi that should be lifting the organs, or the qi-and-yin that should be sustaining the pulse. Notice how these formulas cross concern boundaries: Buzhong Yiqi Wan is discussed for chronic fatigue (stress), Yupingfeng for recurrent colds (immune), and Shengmaiyin for the exhausted-and-dry feeling that shows up under both stress and sleep concerns. That cross-cutting is exactly why this pattern exists as a tag — the same "low fuel" logic connects formulas a Western reader would otherwise see as unrelated.