What are normal ranges for cortisol dex suppression test?

Less than 2mcg/dL: The overnight dex suppression test involves taking 1 mg of Dexamethasone at 9 pm. The morning cortisol drawn at 7-8 am should be less than 2 mcg/ dl.

Cushing's syndrome: In the low-dose overnight test, if the conc. Of am serum cortisol is between 1.2 and 14.3 mcg/dl, the test is equivocal. If >14.3, probably has cushing's syndrome, and further tests needed to confirm. In patients with equivocal results, 2mg low-dose suppression test is used. In overnight high-dose test, the 8 am serum cortisol conc. Is <5 in pts with cushing's dz and undetectable in normal pts.