The amount of sleep that people require does vary from person to person. However, you are really on the far end of the spectrum in terms of the amount of sleep you are getting. It is unlikely that you need that amount of sleep. In general, most physicians say that you need at least 7 hours, but probably more like 8 to 9 hours of sleep per night to be fully rested. Anything above that is probably a waste of time, and may even be harmful. Studies on people that get more than 9 hours of sleep are not really that prevalent. However this is some information that suggests that getting as much sleep as you do may slow your thinking process down some. If you are truly tired throughout those 12 hours that you are awake, then I do think that you should have a workup for why you are so fatigued. If you were my patient, I would probably get some basic blood work to make sure that you are not anemic, and that your thyroid gland is working okay. The best physician for you to see about this problem is your primary care physician
. I suggest that you schedule an appointment soon so that you can this figured out.