In vivo testovi toksičnosti obuhvaćaju testiranja na životinjama i klinička ispitivanja. Testovi na životinjama provode se u laboratorijima, na za to namijenjenim životinjama. Vrsta životinje odabire se prema potrebama i ciljevima eksperimenta. Zbog nerijetkih slučajeva životinjskog trpljenja teške boli tijekom eksperimenata i zbog sumnje u mogućnost primjene tako dobivenih rezultata na čovjeka, često se dovodi u pitanje etičnost tih postupaka. Postoji više vrsta testova toksičnosti, a razlikuju se u svom cilju, te u trajanju i načinu provođenja. Klinička ispitivanja nešto su blaži slučaj in vivo testova obzirom da se provode na izabranim skupinama ljudi, uz vrlo stroge kontrole, te mogućnost subjekta da u bilo kojem trenutku odustane. Dizajnirano je mnogo različitih kliničkih studija, za njih se stvaraju precizni protokoli prema kojima se provode, te se često sastoje od nekoliko faza, svaka sa svojom statističkom snagom i značajnosti.

In vivo toxicity tests include animal testing and clinical trials. Tests on animals are conducted in laboratories, using obtained animals. Animal species are selected according to the needs and goals of the experiment. Because of the frequent cases of animal suffering severe pain during the experiments and because of doubts about the applicability of the obtained results to humans, the ethics of these procedures is often questioned. There are several types of toxicity tests which differ in purpose, duration and manner. Clinical trials are somewhat milder case of in vivo tests as they are conducted on selected groups of people, with very strict control and the possibility of undertaking to withdraw at any time. Many different clinical studies are designed, precise protocols are produced to which they are implemented, and often consist of several phases, each with their statistical power and significance.