What Causes Extreme Fatigue And Confusion?

My Mom has been exhibiting some abnormal behavior for her. She slept very late the other morning and when she got up was very tired all day combined with some mild confusion. She has seen her doctor and her bp is ok. He did blood work which has come back a bit abnormal but he is not sure why. She has an elevated temperature and her eyes feel tired and heavy. It is a week almost now and she is still tired. She is forgetting names that she uses often and in conversation is going off on tangents.