The choice of time depends on the location and condition of illness, the category of drugs and the characteristics of disease. Generally speaking, if a disease focuses on the upper-energizer, it is preferable to take drugs after meals; if on the lower-energizer, before meals. Drugs for acute and serious diseases should be taken at any time, while those for chronic diseases taken regularly. Drugs with tonic or purgative action should be taken with an empty stomach, those with sedatives taken at bedtime, and those irritant to the gastrointestinal tract taken after meals. Drugs for malaria should be taken 2 hours before the onset. Besides special requirements are made for few prescriptions. For example, Shizao Tang needs to be taken at dawn, while Jiming San taken just before dawn.