There are numerous applications of graphene in biomedicine and they can be classified into several main areas: Delivery systems, sensors, tissue engineering and biological agents. The growing biomedical field of applications of graphene and its derivates raises questions regarding their toxicity. We will demonstrate an analysis of the toxicity of two forms of graphene using four various biological models: Zebrafish (Danio rerio) embryo, duckweed (Lemna minor), human HS-5 cells and bacteria (Staphylococcus aureus). The toxicity of pristine graphene (PG) and graphene oxide (GO) was tested at concentrations of 5, 10, 20, 50 and 100 µg/mL. Higher toxicity was noted after administration of high doses of PG and GO in all tested biological models. Hydrophilic GO shows greater toxicity to biological models living in the entire volume of the culture medium (zebrafish, duckweed, S. aureus). PG showed the highest toxicity to adherent cells growing on the bottom of the culture plates-human HS-5 cells. The differences in toxicity between the tested graphene materials result from their physicochemical properties and the model used. Dose-dependent toxicity has been demonstrated with both forms of graphene.