The present work is the study of the different methods used to determine the toxicity produced by the presence of a contaminating metal in the blood. Mainly, the presence of lead in the blood was taken as a reference to focus the work, knowing that metals like Cadmium (Cd) and Mercury (Hg) are also toxic to health and the environment. Although the information is extensive on the methods to be studied and in some cases it is not detailed to define each process, a comparative study of the most relevant and currently used methods can be carried out, taking into account that the choice will be defined according to the main characteristics of each one. Although all agree to be electrochemical processes, there are details to know which method to choose, either by sensitivity, economic or even structural factors, such as having a laboratory for its development. Environmental pollution with toxic elements is very harmful to health, even in small quantities can be very dangerous. These can be present in rivers, soil and even in the air, and these spaces are more than enough to contaminate the human being since these particles adhere in both cases for many years. It is a problem until today and therein lies the importance of the study.