Could .1mg of fludrocortisone cause high cortisol on its own? on it for dysautonomia

More the opposite: Actually, the more common effect on cortisol is to see it lowered since the adrenal cortex tends to get shut down in the presence of chronic doses of Florinef (fludrocortisone). Remember, Florinef (fludrocortisone) is a synthetic equivalent of cortisol. You can watch cortisol levels rise as you begin to decrease to taper off Florinef (fludrocortisone).