“Are there people sick among you? Let them send for the priests of the Church, and let the priests
pray over them anointing them with oil in the name of the Lord. The prayer of faith will save the sick persons,
and the Lord will raise them up. If they have committed any sins, their sins will be forgiven them.” (James 5:14-15)
"The Sacrament of the Anointing of the Sick is given to those who are seriously ill by anointing them on the forehead and hands with duly blessed oil..." (Lumen Gentium - Second Vatican Council)
In the Catholic Church this sacrament was occasionally called "Extreme Unction" and associated with "Last Rites" because people often waited until the moment of death to receive it. The sacrament of Anointing of the Sick is not only given to those at the point of death. It can be administered to anyone struggling with a serious illness to give them strength and healing they need. It is not regularly repeated unless one's condition worsens, one falls into a different serious illness, or, after recovering, falls seriously ill yet again.
The Catechism states, "If a sick person who received this anointing recovers his health, he can in the case of another grave illness receive this sacrament again. If during the same illness the person's condition becomes more serious, the sacrament may be repeated. It is fitting to receive the Anointing of the Sick just prior to a serious operation. The same holds for the elderly whose frailty becomes more pronounced." (CCC 1515)
The healing that occurs in this sacrament of anointing is not necessarily physical healing. The sacrament is given for spiritual healing and grace is given to the recipient so that they may find strength, peace and courage that are needed in the face of serious illness or the frailty of old age. (CCC 1520) In old age and serious infirmity one can easily find their souls sick or weak, easily discouraged, downcast, despairing, and in need of spiritual healing. This sacrament helps us against these temptations of the evil one.
In the bible, James also indicates that this sacrament brings "forgiveness of sins." This has been understood as forgiveness of venial sins, since the Sacrament of Confession is the ordinary way in which our mortal sins are forgiven. There is no doubt that physical healing can arise through this sacrament, as has happened many times, but physcial healing is not the primary purpose of this sacrament.
Avoid waiting until the moment of death or until somebody has died to request this sacrament. Sacraments are for the living and are no longer helpful to those who have died. Try to call when a person's health is noticeably declining and preferably when they are still conscious and responsive. However, in an emergency call your parish priest, or if unavailable, call any Catholic priest as soon as possible.