I had blood fasting cortisol test come back double normal amount. 24 hr urine test is within normal range. why would it be different?

24 hour -better test: The level of cortisol in the blood fluctuates during the course of the day and can spike from stress or pain (like getting your blood drawn), so a blood cortisol level tells us very little unless you are given a pill ahead of time to intentionally lower your cortisol and it stays high anyway. That is called a suppression test. We either use that or the 24 hour urine to screen for excess cortisol.