24-hour urine free cortisol

What this test is

This test collects all your urine for 24 hours. It measures the cortisol your body clears out that day. This can show more than one blood draw. It is used to look for Cushing's syndrome, an illness with too much cortisol. Your doctor will only order it if you have clear signs, like odd bruising, stretch marks, or weak muscles, along with tiredness. One collection alone is not enough to prove a diagnosis. Doctors usually want two collections, or a second type of test, before deciding. Without those clear signs, this test is unlikely to explain plain tiredness.