This usage is in contradistinction to localized hypoxia, in which only an associated group of tissues, usually with a common blood supply, are affected, usually due to an insufficient or reduced blood supply to those tissues.

However, hypoxia may be present without hypoxemia, and vice versa, as in the case of infarction.

[3] Generalised, or hypoxic hypoxia may be caused by: When breathing the ambient air at high altitudes (above 3048 metres/10,000 feet), the human body experiences altitude sickness and hypoxemia due to a low partial pressure of oxygen, decreasing the carriage of oxygen by hemoglobin.

This is a function of the partial pressure of oxygen in the breathing gas, and is also dependent on level of exertion which affects the oxygen requirements of metabolism, cardiovascular fitness, and acclimatization to altitude which affects the available hemoglobin and can vary significantly between individuals.

Where there is no underlying pathology, provision of oxygen at normobaric partial pressure (about 0.21 bar) is usually sufficient to reverse minor symptoms.