What are possible reasons for normal cortisol levels in the blood but high levels in the urine?

Need More tests. A single blood sample may not accurately reflect cortisol levels as peak values may have occurred at a different point during the daily cycle, producing a normal blood sample when cortisol levels are actually elevated. The elevation would be detected, however, by 24-hour urine cortisol levels. High urine cortisol can be caused by cushing's, lung cancer, adrenal tumors.