A cortisol blood test is conducted to discover the cortisol hormone level in the blood. Cortisol assists the body in metabolic process stress management. The levels of cortisol inside the blood are vastly different as a result of several factors like stress, infection, injury and strenuous activities. The levels of cortisol usually vary in the length of your day. In the morning, it's generally increased, and at night and during sleep, its level is often low. Its level, however, may follow the person's sleeping habits. Those who sleep within the daytime and so are awake during the night, could have reversed cortisol level patterns also. The first basic is you are what you eat!