Catechism of the Catholic Church §1514 — excerpt
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."
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: SC 73 · CIC, Cann. 1004 # 1 · 1005 · 1007 · CCEO, Can. 738