Dizziness and nausea may be caused by the following reasons: 1. If dizziness and nausea occur suddenly in middle-aged or elderly people, they may be caused by acute cerebrovascular diseases, such as cerebral vascular spasm, new cerebral infarction or minor cerebral hemorrhage. 2. Dizziness and nausea may also be caused by cardiac diseases, such as malignant arrhythmia or slowing of the heart rhythm. 3. If the dizziness and nausea occur during a specific position change of the head, it may be caused by otoliths. 4. If the patient has dizziness and nausea, it may also be caused by gastrointestinal disorders. If acute gastroenteritis is caused by eating unclean food, it may also manifest as dizziness and nausea.