What condition is referred to as hypoxia?

Hypoxia is a condition characterized by insufficient oxygen supply to the body or specific tissues. In the context of the choices given, the correct answer accurately describes hypoxia as a situation where there is not enough oxygen in the bloodstream, which can lead to symptoms such as a blackout or loss of consciousness. This lack of oxygen can occur at high altitudes, during certain medical conditions, or due to environmental factors.

The other options present related concepts but do not accurately define hypoxia. For instance, the excess of carbon dioxide in the bloodstream typically refers to hypercapnia, which is a different respiratory condition. Feeling dizzy from poor blood circulation might imply a variety of circulatory issues but does not involve oxygen levels directly. Lastly, while prolonged exposure to high altitudes can indeed lead to hypoxia due to decreased atmospheric pressure and available oxygen, the term itself is broader and not solely defined by altitude exposure.