I take one Cortisol Manager (and 3mg of melatonin) roughly 3 hours before bed time each night.

http://www.integrativepro.com/Products/Stress-Sleep-Manageme...

After a few months, I had my cortisol levels retested and it's now "normal", peaking in the morning instead of at night.

http://en.wikipedia.org/wiki/Cortisol#Patterns

I went without for a week, just to see before v after. Seems to help.