The law is short and exact. Canon 919 §1: one who is to receive the Most Holy Eucharist is to abstain for at least one hour before Holy Communion from any food and drink, with the sole exceptions of water and medicine. Reckon the hour to the moment of receiving Communion, not to the beginning of Mass — which in practice means that if you are eating on the way, you have almost always kept it. Water may be taken at any time, and so may any medicine. Canon 919 §3 excuses the elderly, the infirm, and those who care for them: they may receive even if they have eaten something within the preceding hour. Canon 919 §2 allows a priest celebrating two or three times on the same day to take something before the later celebrations even if less than an hour has passed. Keep the fast as a preparation and not merely as a rule: many Catholics extend it voluntarily to three hours, or from midnight, as the older discipline required, and use the time for prayer, examination and an act of contrition before Mass.

The one-hour fast is the discipline of the 1983 Code of Canon Law (c. 919), which relaxed the older and longer fasts. Sacramentum Caritatis places such preparation within the wider reverence owed to the Eucharist.

Fasting

Latin Church

About 1 hour

Before every reception of Holy Communion

fasting