salivary cortisol botoom range is 0.12 not 0.012 thanks
I cannot tell - is this one set of testing or three?
Just testing cortisol is about 30% of the story. You also need to know ACTH (it is the other half of the loop), sodium and potassium (and if abnormal, renin and aldosterone) as well as other hormones and antibodies.
Fatigue is a non-specific symptom. It cannot be attributed to just low cortisol as it can be attributed to tons of disorders (including high cortisol!).
As for cortisol needing to be in the upper part of the range... be careful of what you read and where. Is this a reputable medical site? Cortisol normally varies - it is called the circadian or diurnal rhythm so people and time vary. It does help to test more and test at different times of the day (like midnight) to know if you have, say, a reversed rhythm.
A stimulation test is also useful to know. But if you are borderline, you may pass until the adrenals have fully atrophied. It is very complex. Thyroid can also make you very fatigued if you are under treated.
the three samples where taken on different days independently