What Causes Numbness And Tingling On Hands And Feet?

As of the last two days my hands and feet have been numb and tingling. I have never had this before. It's not going away. I went to the hospital and had a cat scan and blood work. They said they couldn't find the problem and released me. I am 5'8 250 lbs and have no medical conditions other than the above. I do not take any drugs or prescriptions other than avelox last week for a sore throat.