How long to boil herbs needs to be different depending on the nature and type of herbs, the method of decoction and the time of boiling. Under the guidance of a doctor, Chinese herbs bought from a pharmacy should be soaked in cold water for 20 minutes and then used in a casserole to simmer, first turning on medium heat and boiling then turning off low heat for 30 minutes. For the treatment of common chronic diseases, such as spleen and stomach diseases and hypertension, the first decoction is boiled and then turned off the medium heat for 20-30 minutes, and the second decoction is boiled and then decocted for about 15-20 minutes. For the treatment of deficiency tonic herbs, turn off the low heat after the first decoction boils for about 30-40 minutes, and the second decoction boils for another 20-30 minutes.