Toxicity is always an issue to be covered when supplementing as there are some chemicals that walk a fine line between benefiting and damaging your body. Nootropics in particular happen to be known for having an extremely low toxicity in most cases. It is possible to not only overdose, but go much farther then that. Studies to find the toxicity levels of racetams led to very optimistic results. When tested on rats through IV, they reached levels as high at 8g/kg and orally up to 10g/kg with no toxic effects.
This can translate to roughly 1 to 1.5 pounds of chemical for a 150 pound man to dose. This and other studies brought scientists to consider chemicals such as these “safer then salt” and can be taken almost ad nauseum. If a supplement I study and write on is dangerous in higher doses that does not mirror the toxicity of nootropics I will state so.