Cortisol level interpretation

Posted by beanie300 @beanie300, Jul 3, 2019

About three months ago I was seen at the Mayo Clinic in Rochester for extreme fatigue. They found that my cortisol was low, a 5.8 with a reference range of 7-20 (the blood was taken at 10am). I was told to follow up with my regular doctor in three months, which I just did, to have another cortisol test. My doctor said if it came back low again I would be referred to an endocrinologist. This time it came back a 4.8, even lower than last time. Blood was drawn at 8:30am. However, I just got a letter from my doctor saying my cortisol looks like it’s back within normal range, with the reference range listed at 4.8-20. Can someone maybe explain to me how the reference range changed? This isn’t me being sarcastic, I genuinely want to know how the reference range could change like that. I know cortisol levels vary throughout the day but I was told they are supposed to be highest that early in the morning or something like that. I’m too afraid to ask my doctor about it because I have gone through so many doctors now trying to figure out what is wrong and I don’t want my doctor to think I’m a hypochondriac or something so I figured I would ask here. Thank you in advance to anyone who can give me any info on this!

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@beanie300, I would be as confused as you are. This reference from the University of Rochester Medical Center confirms your understanding about reference levels and time a day fluctuations.
– Cortisol

I encourage you to ask your doctor about the interpretation of the results. Also inquire whether the results will be forwarded to your doctor at Mayo Clinic.


I am having the same issue. I recently had a tumor removed from or attached to my pituitary gland. My cortisol levels have ranged from 20 (pre-surgery) to 15 (post-surgery) and in between. My doctor says I have adrenal insufficiency but when I get test results results back they show me in the normal range. I don't know what or whom to believe. Is there an acceptable level of cortisol? All of my tests have been done in the early morning. I have also been told that I need to get a medical alert bracelet for this condition.

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