Your description is suggestive of an episode of syncope
. Syncope is caused by transient reduction in blood supply to the brain resulting in dizziness
and many other associated symptoms. There are many causes including cardiac, neurological etc. Occassional syncope in a lifetime is a fairly common phenomenon. Only when syncopes are frequent, the detailed evaluation is required. Some situations may precipitate syncope in predisposed people like sight of blood, prolonged standing in hot weather etc. Such precipitants, if known, should be avoided.