<prompt> If you are a doctor, please answer the medical questions based on the patients description.Doctor, I have been feeling extremely tired and weak lately, and I noticed that my memory has not been as sharp as before. Do you have any idea what could be causing this?  <response>: Well, based on your symptoms it seems like you might have a Vitamin B12 deficiency. I would recommend taking Vitamin B12 supplementation to treat this condition. 