Chapter — Slater, Manual of Moral Theology
Chapter III. The Recipient of Extreme Unction
IN order to be able to receive Extreme Unction validly a man must be baptized, must have attained the use of reason, and must be in probable danger of death from sickness. Extreme Unction, then, may be administered to those adults who are in danger of death from disease, from the pains of childbirth, from a wound, from poison, and from old age, even though they be no longer in their right senses. It cannot be validly given to soldiers before going into battle, to criminals who are going to be executed, to imbeciles who have never had the use of reason, to children who have not yet come to the use of reason, nor to unbaptized persons.1
1 Ritual.
p. ii, 182
This sacrament may only be given once in the same sickness and in the same danger, but if the sickness be prolonged and after partial recovery the sick person again becomes dangerously ill, Extreme Unction may be repeated. According to some good authors, it may be repeated after a month’s interval, for as a general rule the danger may be considered a new one after such a period of time.
No good Catholic would wish to depart this life without the help of this and the other sacraments; still there is no obligation under grave sin to receive Extreme Unction. But although the faithful who, without despising it, neglect to receive this sacrament do not thereby commit grave sin, yet a priest who has the cure of souls would sin grievously if he neglected to give those under his charge the opportunity of receiving this sacrament in their last sickness. As soon as there is probable danger of death the last sacraments may be given in the following order: Penance, Viaticum, Extreme Unction, and finally the papal blessing for the moment of death.
Canon 941 prescribes that when it is doubtful whether a sick person has attained the use of reason, whether he is really in danger of death, or whether he is dead, this sacrament should be administered conditionally.
p. ii, 182