Hypoglycemia, or low blood sugar, often results in an insufficient level of glucose in the brain. The condition causes a number of symptoms including dizziness, anxiety and palpitations. A source told People, "Four or five times [Nicole has] felt really faint [while filming] and almost passed out. She has to go into her trailer for a good part of the day."

Nicole, who has been working on the fifth season of her reality show with Paris Hilton "The Simple Life," has had continuing battles with her weight, but denies having an eating disorder. Many thought Nicole's frail figure was responsible for her recent hospitalization.