why to do serum cortisol test
1 Blood/Serum. 2  A cortisol test is done to measure the level of the hormone cortisol in the blood, which may indicate problems with the adrenal glands or pituitary gland. 3  Ideally, perform the test around 8:00 a.m., and aim for the optimal range for adults of 10-15 mcg/dL.hen it comes to cortisol testing, here are the best options. 1  Blood/Serum. 2  A cortisol test is done to measure the level of the hormone cortisol in the blood, which may indicate problems with the adrenal glands or pituitary gland.