I need 9.5 hrs of sleep to function but blood tests are normal. What could be wrong with me?

Depends -variousneed. Infants need 14-15 hrs, toddlers 12-14, children 10-11, adults need 7-9 hrs if you had sleep deprivation your needs will be higher also if you do not get enough dream sleep REM sleep you do not get effective sleep. Holistic perspective if there is problems with gall bladder this will interfere with sleep have this checked out.
See a sleep doctor. You should see a sleep doctor. Hypersomnia may be due to an underlying neurologic disorder. Keeping a sleep log may help determining if you are in bed for too long and not sleeping or actually sleeping for that duration of time. Bottom line, I would have you see a sleep doctor your area - pulmonary medicine. You can also look for a sleep lab. They all have board certified sleep doctors.