BACKGROUND This case report illustrates the difficulties that arise during diagnosis of adrenal insufficiency, especially in the general medicine setting. Symptoms can often be nonspecific, and when a serum cortisol level is checked, further difficulty exists as to how to interpret the results. The 250-μg cosyntropin dose or 1-μg dose are available for use in the diagnosis of adrenal insufficiency, but each test has its own indications, which will be discussed. CASE REPORT A 45-year-old woman presented with nausea, emesis, chills, and diaphoresis, symptoms that concerning for adrenal insufficiency. Her random serum cortisol levels were relatively low. Her ACTH levels were within normal range. She received additional testing with the ACTH stimulation test using both the 1-μg and the 250-μg dose. The 1-μg test was performed in the evening and showed an inadequate adrenal response. The 250-μg dose test, which is the criterion standard, was performed the following morning and excluded adrenal insufficiency. CONCLUSIONS With the use of the high-dose ACTH stimulation test performed in the early morning, this patient was able to avoid lifelong steroid replacement therapy that could potentially suppress the hypothalamic-pituitary-adrenal (HPA) axis, which of itself can lead to adrenal insufficiency. Careful consideration is needed in choosing the right modalities for diagnosis of adrenal insufficiency.