I feel tired all the time even when i get 8 hours of sleep. what is that?

Fatigue: Check previous answers under " fatigue "or "lack of energy"or "tiredness".

I am so tired, tired: Sleep quality is best ascertained by asking yourself in the am, "am i rested?" if you move around alot in your sleep, snore/gasp, or seldom dream, you may have a sleep disorder. Persistent fatigue has innumerable causes including depression, seasonal affective disorder, medications, anemia, hypothryroidism, substance abuse, or any of a number underlying medical problems. Consult your md.

Anything: You can have sleep problems from snoring, apnea, restless legs, poor sleep hygeine, anxiety/depression, napping during the day, night seizures, noises in the neighborhood waking you up, bed bugs, waking up to use the bathroom, acid reflux, allergies, or any number of things. I recommend seeing a doctor to get checked out.