Can my regular doctor do the fecal fat test in his clinic?

Maybe... Fecal fat testing can be performed qualitatively (to see if fat droplets are present) or quantitatively (to measure how much fat is lost in stool). The former is a simple slide test using a sudan stain on a random stool sample, whereas the latter needs a timed collection of stool for measurement. Both studies are somewhat specific, & outside the usual in-office tests primary care docs might run.