text: what could cause a non-anemic person to have no energy? i have been tested for anemia and for thyroid problems but both come back as ok.  i take vitamins and try to eat well but i could sleep 12 hours and wake up feeling ok for about 3 hours and then i can hardly keep my eyes open after that point.  not good when you have to work 8 hours a day. i've heard of times when a person's thyroid test came back looking basically okay, but there's a sub-clinical problem that won't show on a blood test. i think they do a thyroid biopsy, and can get answers from that. also, you could have a sleep disorder- yes, you're sleeping, but maybe not getting enough restorative sleep. depression can cause fatigue. and chronic fatigue syndrome (which i was diagnosed with) could be the problem, but is not something that there's a test for yet, and there's no real cure for it at this point. i think a vitamin b deficiancy can cause fatigue too. and untreated diabetes, but that would have other symptoms too, and may not cause the tiredness after a few hours of working. for more chronic fatigue info. maybe try this link:   http://www.nlm.nih.gov/medlineplus/chronicfatiguesyndrome.html