Qi deficiency refers to the weakness of healthy qi in human body. Two main reasons account for qi deficiency: 1) insufficiency of qi transformation, e.g., the deficiency of prenatal essence may lead to the deficiency of original qi; spleen-stomach weakness may result in deficiency of essence from food and drinks; or the failure of lung qi in dispersing and descending may reduce the inhalation volume of fresh air; and 2) excessive consumption of qi, e.g., excessive lassitude, exogenously-contracted febrile diseases, or chronic consumptive diseases may lead to over-consumption of qi and consequently qi deficiency. Clinical manifestations of qi deficiency include listlessness, fatigue, disinclination to talk due to the lack of qi, dizziness, spontaneous sweating, pallor complexion, pale tongue, and feeble pulse.