Tonic herbs are safe to consume regularly over long periods of time.  The Chinese refer to these type of herbs as superior herbs since they are prized and promote longevity, beauty, and vitality.  It is preferred to prevent disease rather than try to fix it in the Chinese cosmology.  There are roughly 120 herbs in this category.
Medicinal herbs are used for shorter periods of time and should only be administered under a physicians care.  They are used for specific reasons and not general health promotion.  While some tonic herbs are used in medicinal formulas as well, they are used differently medicinally.