The medicinal herbs moderate in nature can be used in a large amount; those drastic or poisonous in nature must be used in a small amount; those light in property should be used in a small amount; those heavy in property, such as mineral and shell but without toxin can be used in a large amount; fresh plant medicinal herbs, since they contain water, should be used in amount about twice as much as that of dry ones.

The amount of a singly used herb is usually large than that compound ones in a prescription; the amount of a main ingredient in a prescription is larger than that of an accessory one; the amount of a medicinal herb in making decoction is larger than that in pills or powder. For instance, Rougui (Cortex Cinnamomi) used in decoction usually weights 3 g, but if used in pill or powder, it is only needed 0.5 to lg.  

3．The condition of illness, the patients' physique and age   

The amount of a medicinal herb used in the treatment of serious and acute disease must be fairly large while the amount used in the treatment of the mild or chronic comparatively small. The amount used for those with strong physique must be large while for those with weak physique, the old and children, the dosage generally small. For children over 6 years, half the dose of an adult''s is used; for the children below 5 years, 1/3 - 1/2 dose of an adult's is used; for an infant, the dosage should be much smaller.  

 

Besides, the dose of expensive medicines under ensurance of medicinal effects should be small, such as, Shexiang ( Moschus Artifactus ), Niuhuang ( Calculus Bovis),etc., and we should avoid waste of medicinal materials and economic burden on the patient. The dose must be used flexibly according to the differences of patient's physique and areas, climates, and seasons, etc.