A safe and effective echinacea dosage has not been established. Different products may contain different species of echinacea and different amounts of the supposed active compounds of echinacea, so there is no standard recommended dosage. Since there is little information to guide you in choosing an appropriate echinacea dose, it is best to follow the dosing instructions on your particular product.
As with most herbal supplements, the best (most effective and safe) doses for echinacea have not yet been scientifically established. However, basic dosing guidelines can be obtained from clinical studies of the supplement.
With prescription and non-prescription medications, researchers establish the most effective and safe doses in special studies, known as dose-range studies. These studies are done early in the development of medications, long before they are ever approved. However, because dietary supplements do not need to be approved by the U.S. Food and Drug Administration (FDA), dose-range studies are rarely performed. Without such studies, only vague "trial and error" information is typically available.
Even if clinical studies are available, as is the case with echinacea, these are rarely the right types of studies to determine the best possible dosage.
To make matters even more complicated, different products may contain different species of echinacea and different amounts of the supposed active compounds of the plant. Also, studies have shown that some echinacea products contain significantly less echinacea than labeled, and some may even be contaminated with lead, arsenic, or other contaminants.
Because there is so little good information to guide you in choosing an appropriate echinacea dosage, it is probably best to simply follow the dosing instructions on your particular product.