The classification of qi in the human body varies with its distribution, origin, and function.

1. Primary Qi (yuan qi)

Primary qi is the most important and fundamental qi originating from the congenitalessence. It is nourished and replenished by the fundamental substance of food after birth. Primary qi is also known as the qi of the kidney, and is distributed to the whole body via the sanjiao functions. It arouses and promotes the activities of the zang-fu organs and tissues. If primary qi is congenitally deficient or exhausted due to chronic disease, then various pathological changes will occur.

2. Aggregative Qi (zong qi)

This is the combination of inhaled clean qi through the lung with the fundamental substance qi of food digested and absorbed by the stomach and spleen. Aggregative qi is accumulated in the chest and has the function of nourishing the lung and the heart, thus promoting respiration and blood circulation.

3. Nutrient Qi (ying qi)

Nutrient qi originates from the essential substance of food transformed by the spleen and stomach. It is the component part of blood flowing throughout the body. The Suwen states, "Nutrient qi is actually the essential qi transformed from food and water." While in the Lingshu it is recorded:

The nutrient qi is secreted by the body fluid, circulates in the blood vessels, and is transformed into blood to nourish the four extremities, the five zang and six fu organs.