• Variation in absorption and metabolism of dexamethasone (e.g., P450 enzyme system interactions, liver or renal disease) between patients may influence results• False positives in women taking oral contraceptive pills and during pregnancy due to increased cortisol binding globulin (CBG)• Poor performance in differentiating from nonneoplastic hypercortisolism• Incompliance may cause a false-positive result• No possibility to test cortisol levels in retrospect as is useful in cyclic CS. Here, CYP2B6 is linked to kidney disorder.