He was born in Koper on 29 March 1561 to Antonio, of Friulian origin, and Elisabetta Cordonia, from Koper. Antonio, the father, serves the Serenissima as an ammunition supermassaro and at an early age Santorio moves to the lagoon city with his brother Isidoro, while the sisters Piana and Franceschina remain in Koper where they get married.
In Venice he was able to study humanities thanks to the support of the Morisini patricians, friends of the Sartorio family, and in 1575 he carried out philosophical studies with Giacomo Zabarella and medicine with Bernardino Paterno; during these years, he established relationships of trust and friendship with the future Doge Nicolò Contarini.
Having obtained his medical degree in 1582, Santorio becomes prince of the Palladian Academy of Koper and apparently travels around Europe, staying in Hungary and Croatia. It is assumed that during these trips he comes into contact with the Archduke Ferdinand of Styria - the future Ferdinand II - to whom he dedicates his first printed work, the Methodus vitandorum errorum omnium qui in arte medica contingunt libri XV (Venice 1603), who it contains a strong reference to experience, rather than to the undisputed authority of the ancients, aimed at developing a method that avoids all errors in medicine.
As early as the early seventeenth century, Santorio moved permanently to Venice where he cultivated a close network of friendships, as well as with the historian Andrea Morosini also with the patricians and anti-clerical intellectuals, who would later be protagonists of the Interdict dispute, like Nicolò Contarini and Fra Paolo Sarpi.
On 5 October 1607 Paolo Sarpi suffers an attack and Santorio is among those who, inside the convent, give him the first medical care. Their friendship is really strong if you consider that the brother also involves the Koper in reading and discussing forbidden books. Thanks to Sarpi, Santorio has access to Galilean studies, very useful for his medical career, and to meet Galileo Galilei himself as well as some of his Venetian admirers such as Giovan Francesco Sagredo, Agostino Da Mula and Giacomo Barozzi.
The right attendances, the progress and the inventions of new medical instruments, a Santorio to obtain in 1611 a chair in theoretical medicine Studio of Padua for the duration of six years, with a salary of 800 silver ducats, raised to 1200 from 1618 to 1624. In these years, Santorio achieved a European fame for his studies and his publications, becoming the precursor of that new medical school that will take the name of iatromechanics (also known as iatrophysics) and that has influenced modern medicine: he tries to quantitatively reduce phenomena such as human metabolism and fever.
From these studies new instruments have emerged, such as the pulsilogium - a sort of chronometer that can measure the heartbeat of the pulse, the medical thermometer for measuring body temperature (it is still a matter of dispute whether the invention of the thermometer in general is from to attribute to Santorio or to Galileo), and his fundamental work: De statica medica (Venice 1614), of which he gives a copy to Galilei.
The work collects the results of thirty years of observations and experiences, through the use of a balance chair built for the purpose, which we can consider the mother of modern body weight scales, through which it wants to demonstrate that any alteration inside the human body it corresponds to a change in weight - therefore subject to experimental analyzes and quantifications. What Santorio understands is that the human body is in fact a living laboratory, where digestion serves to separate and recombine ingested food and drinks, in order to translate them into nutrients useful to the body, urine and feces, as well as micro particles that are expelled from the body through insensitive sweating through the skin pores and respiratory tracts.
It can therefore be said that his studies and publication changed European science - influencing generations of physicists and philosophers across Europe - with more than 84 editions in about 100 years and translation into almost every European language existing at the time. .
During his stay in Padua, Santorio demonstrates his anti-curial orientation by agreeing to preside over the Venetian College, set up by the Senate to confer the Paduan degree to those who do not want to pronounce the Tridentine profession of faith (such as Protestants and Jews), thus obtaining strong criticism from the papal nuncio Berlinghiero Gessi.
In 1623 Santorio reached his friend Paolo Sarpi in Venice, accompanying him in his death and clashing with a certain hostility: he was attacked several times, even with the accusation of lack of diligence in university teaching - then obtaining an acquittal in 1624 - but he was more likely that the reasons are ideological. Due to these attacks, he renounces teaching in Padua, while substituting his salary until his death.
He spent the last years of his life in Venice, residing in the parish of San Marcuola and privately practicing the profession of doctor. During August 1630 he was consulted by the Senate for a medical opinion on the disease that was affecting Venice: he answered as the best of the doctors consulted and as is the desire of the judiciary, declaring that the cause is not to be attributed to the plague. Unfortunately, the events that follow will prove the exact opposite.
Santorio died in Venice on February 22, 1636, was buried in the portico of the church of the Servi and bequeathed a considerable patrimony, partly deposited with the Mint, as well as other credits and assets, for a total patrimony of around 70-80,000. ducats.