Cortisol is a hormone that helps with a variety of bodily functions. These include maintaining blood sugar, managing the immune system, regulating blood pressure, controlling some of the electrolytes in the body, and controlling stress levels.
Cortisol levels are highest in the early morning and after meals and the lowest at night in the early sleep phases.
Low levels of cortisol can cause weakness, extreme tiredness, and drops in blood pressure. Most of the time, however, the human body is capable of balancing the amount of cortisol it produces.