"The special grace of the sacrament of the Anointing of the Sick has as its effects: the uniting of the sick person to the passion of Christ, for his own good and that of the whole Church; the strengthening, peace, and courage to endure in a Christian manner the sufferings of illness or old age; the forgiveness of sins, if the sick person was not able to obtain it through the sacrament of penance; the restoration of health, if it is conducive to the salvation of his soul; the preparation for passing over to eternal life" (CCC 1532).
Does a person have to be dying to receive this sacrament? No. The Catechism says, "The anointing of the sick is not a sacrament for those only who are at the point of death. Hence, as soon as anyone of the faithful begins to be in danger of death from sickness or old age, the fitting time for him to receive this sacrament has certainly already arrived" (CCC 1514).