This is another issue muddied by a lack of formal regulation and the fact that CBD, CBDA, and other hemp-borne cannabinoids are administered in high and/or widely varying doses in studies (from as low as 20mg or so to more than 500mg a day). These make for very vague dosage parameters, but starting small and working up based on results is a tried-and-true method that keeps safety at the forefront. You can consult this CBD Dosage Chart to learn more.