I started taking the cephalexin last night for bronchitis. When I go to the bathroom, my stools are rusty red color. I am not sure if this is blood or discoloration due to the medicine. I talked to my doctor and pharmacist. My doctor thought this was unusual. He wants to wait and see because he is concerned that it could be blood. So until this clears up, he will not prescribe another antibiotic. This is kind of frightening because of the first thing you think when your stool is red/blood you assume the worst. Still I think whether it is blood or discoloration it must be the med because it didn't start until after I took it. My stomach is a little queasy and bowels are slightly lose still. I'm still worried.