ZeTox – Toxicology Services


icon-fast-acute-toxicity Fish Embryo Acute Test (FET)

Fish Embryo Acute Test is a method that uses zebrafish embryos to determine acute toxicity of chemicals and, therefore, to assess the safety of compounds.


High throughput screening of compounds.

Applicable to a wide range of compounds regardless of the mode of action, volatility, solubility, and hydrophobicity.

Simultaneous assessment of developmental effects.

Highly predictive for acute toxicity effects in humans.

Method description

Incubation of embryos with 5 different concentrations of the molecule of interest spaced by a constant factor 2 from 0 to 96 hours post fertilization (hpf). Assay performed according to the OECD guideline 236.


Determination of the following parameters at 24 and 96 hpf:

  • LOEC: Lowest Observable Effect Concentration
  • LC50: Lethal Concentration 50 Survival
Figure: Representative images of zebrafish larvae exposed to increasing concentration of a toxic agent at 24 and 96 hpf.


  1. OECD. 2013. Test No. 236: Fish Embryo Acute Toxicity (FET) Test.