I don't really know what exact safe dosages are, if you eat any fish or seaweed products, then this is probably plenty. There is a very powerful herb that stimulates the thyroid called ashwagandha that is used in ayurvedic medicine, but it is not for everyone and is prescribed only for certain people, others can have problems when taking this. In ayurveda, we only use herbs under the direct supervision of a qualified practitioner, otherwise you could be doing more harm than good.