does coffee affect cortisol levels?
âTherefore, if we are drinking caffeine at a time when your cortisol concentration in the blood is at its peak, you probably should not be drinking it.â. Those who drink coffee when cortisol levels are high â commonly between 8 a.m. and 9 a.m. â are more likely to develop a tolerance to caffeine. This increased tolerance means the drug will become less effective in the body.