Midnight Serum Cortisol is a simple blood test that can be a good diagnostic tool for Cushing's Disease or Syndrome. You see, cortisol should be at it's lowest point around midnight in a healthy person, so it is a good time to test for excess because the range for "normal" is so small.
It's a simple blood draw like any other, though at least the fist one should include a serum ACTH (will be addressed in a future post) to get a better picture of what is happening with your pituitary and your adrenals. These results come back quickly, too (BONUS! No 2 week wait!).
The difficulty in this test is getting the lab to draw them. I had great luck locally contacting the hospital's lab manager, explaining the test my doctor ordered, and requesting they draw it. I explained that I would happily come in 30-60 minutes early and stay 30-60 minutes late should they be busy, giving a decent draw window for their one tech on duty at that time of night (It's a small hospital). I was very lucky and they agreed to do it.
I did have to enter through the ER entrance, but the security guards and ER nurses recognized me quickly (I did a series of 4 nights in a row) and admitting staff had been told I would be coming in for testing and thus admitted me as outpatient. The diagnostic cutoff typically is 7.5 for a midnight draw. Anything above that is considered diagnostic. For a sleeping midnight draw (if you were spending the night at the hospital in their bed), the diagnostic cutoff is actually only 3.
Personally, I love this test. I think the timing is still more convenient (and the results faster and more universally accurate) than the inconvenience and shortcomings of the 24 hour urine tests.
(Note: it is also worthwhile to have had a CBG recently, as that can affect a total serum cortisol draw --more details in a future post).