Hypoxia is a condition characterized by an inadequate or decreased supply of oxygen to the lungs. It is caused by several extrinsic factors such as the reduction in ${\mathrm{pO}}_2$, inadequate oxygen, etc. The different types of hypoxia are discussed below. 

Hypoxemic hypoxia
In this condition, there is a reduction in the oxygen content of blood as a result of the low partial pressure of oxygen in the arterial blood.

Anemic hypoxia
In this condition, there is a reduction in the concentration of hemoglobin.

Stagnant or ischemic hypoxia
In this condition, there is a deficiency in the oxygen content of blood because of poor blood circulation. It occurs when a person is exposed to cold temperatures for a prolonged period of time.

Histotoxic hypoxia
In this condition, tissues are unable to use oxygen. This occurs during carbon monoxide or cyanide poisoning.