They say acknowledging an event as a miracle must be supported by either five-out-of-seven members of an examination board, or four-out-of-six members.
In a statement, the Vatican said: "The purpose of the Regulation can be none other than the good of the Cause [the body which oversees the canonisation process], which can never neglect the historical and scientific truth of the alleged miracles."
The new regulations, which govern the Medical Board of the Congregation of the Causes of Saints, also stipulate a case may be re-examined no more than three times, and each re-examination requires a board of at least nine members.
The advice of medical experts has been sought in the process of canonisation within the Roman Catholic Church since 1743, however the regulations have since been updated many times.
According to the latest changes, the five year term of the Medical Board's president can now only be renewed once.
The rules also state the salary for medical experts shall only be paid via bank transfer, while deliberations over an apparent miracle are to be held in secret.
The Vatican added: "This Regulation obviously concerns only the good functioning of the Medical Board, whose task appears increasingly delicate, demanding and, thanks be to God, appreciated both inside and outside the Church."
The pope, who celebrated the canonisation of Mother Teresa earlier this month, has ultimate control over who is declared a saint.
The pontiff has also embarked on a Holy Year of Mercy, encouraging Catholics to focus on God's mercy.