What's the most practical way to rule out adrenal insufficiency?

Abstract

A morning serum cortisol level >13 mcg/dL reliably rules out adrenal insufficiency, and the test is easy and safe to perform. Because of low specificity, patients with a level of ≤13 mcg/dL need further evaluation with the cosyntropin stimulation test (CST) (strength of recommendation [SOR]: A, meta- analysis of diagnostic cohort studies).