Morning cortisol or stimulation tests can be repeated every few months until the morning cortisol level is greater than 18 micrograms/dL, or the appropriate stimulation test confirms hypothalamic-pituitary-adrenal axis integrity.
epocrates
...Or you fall into the bad zone.
I think I've read that some doctors put people on a trial of medicine if they are lowish and symptomatic.
Note: micrograms/dL = ug/dL
I wonder what the next test would be if you fall in the "indeterminate" range. Hmmm....
"Cortrosyn is a synthetic corticotropin, which is intravenously administered with a dose of 350 mg. Serum cortisol levels are measured from blood samples drawn after 30 and 60 minutes. Peak serum cortisol levels greater than 18 mcg/dL exclude the diagnosis of adrenal insufficiency because the response to stimulation is considered adequate at this level. Cortisol levels of 13-17 mcg/dL are indeterminate. Cortisol levels of less than 13 mcg/dL suggest adrenal insufficiency."
emedicine
To get diagnosed, the doctor should do a stim test.
Are you giving a result for a point in time test, or a stim test result? If stim test, where are the other results? Usually there are a couple others.