Nausea is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It may precede vomiting, but a person can have nausea without vomiting. Nausea can be due to motion sickness, dizziness, migraine, fainting, low blood sugar, gastroenteritis (stomach infection) or food poisoning.
Nausea can also be the side effect of many medications including chemotherapy, nauseates or morning sickness in early pregnancy. Nausea may also be caused by anxiety, disgust and depression.