How far apart can you take keflex...my dr. told me to take them every 6 hrs 4 times a day but i'm sleeping part of the time and that messes me up ?

Four times daily: Rather than set an alarm to take medication exactly every 6hrs, space out your meds so that you end up taking 4x/d while awake, say 1st time upon waking up, 2nd time around lunch, 3rd time around dinner & 4th time just before sleeping. Yes, some times are closer than others while others are farther apart but I would never tell my patients to take it every 6hrs b/c concerns you've noted.