Blood and Qi have a very close relationship. Blood is said to be is a denser form of Qi, and more Yin in nature.
Qi and Blood are inseparable, and the Ying form of Qi actually circulates with the Blood in the Vessels. While Blood engenders Qi, Qi is said to command or move the Blood.
The dependency of Qi on Blood can be illustrated as follows: After a patient has experienced heavy Blood loss, they will usually show signs of Qi deficiency, such as weakness, sweating, breathlessness, and fatigue.
The dependency of Blood on Qi can be illustrated as follows: After prolonged and heavy sweating injures or depletes the Qi, a patient may develop symptoms of Blood deficiency, with symptoms such as pale face, numbness, palpitations, and dizziness.
Where Qi is deficient, eventually Blood will become Deficient. Where Blood is deficient, one often needs to tonify Qi.
"When Qi moves, Blood follows". "When Qi stagnates, Blood congeals."
When Qi is deficient or stagnant, it fails to push Blood, which also stagnates.
Spleen Qi is responsible for holding the Blood in the Vessels, preventing extravasation. If Spleen Qi is deficient, hemorrhages may occur.
It is said... "Blood is the mother of Qi"
Blood also nourishes and replenishes the Jing (Essence).