We must remember the church teaching that the whole Christ is received under either species of bread or wine. A substitute form of the bread may not be used. Wheat flour contains glutens, to which some are allergic; while bread made with a low amount of gluten may be used, gluten-free bread is not valid for the Eucharist. For those who cannot take even small amounts of gluten, the solution is the offering of the Precious Blood alone.
If a person has received Communion, he or she may receive it a second time on the same day if it is during a celebration of the Eucharist itself. Viaticum, the Eucharist given to a dying person or a person who is danger of death, may always be given regardless of whether or not a person has already received Communion that day.
A priest may use mustum, juice pressed from the grape but not yet fermented into wine, as a substitute for wine if he cannot consume a small portion of wine and has permission from the Chancery Office. Mustum cannot be consumed by the congregation.
A mentally or developmentally challenged person should be appropriately disposed to receive Communion, be able to distinguish the Eucharist from ordinary food, and be able to receive Communion reverently. Parents or guardians and the pastor share the responsibility for the preparation for and the participation in the Eucharist.
Because Catholics believe that the celebration of the Eucharist is a sign of the reality of the oneness of faith, life and worship, members of those churches with whom we are not yet fully united are ordinarily not admitted to Holy Communion. Eucharist sharing in exceptional circumstance by other Christians requires permission from the archbishop.
The communicant may never be allowed to self-communicate, even by means of intinction, or dipping the consecrated host into the wine cup. Communion under bread or wine must always be given by an ordinary or extraordinary minister of Holy Communion.
Prior to reception of Communion, a person should fast from food and drink, with the exception of water and medicine, for at least one hour. The elderly and the sick, as well as those who care for them, are not required to maintain the hour’s fast.
Canon law requires that the bread be recently-made wheat bread so that there is no danger of spoilage. Bread made from flour other than wheat or with other additives is not valid for the celebration of Eucharist. Ancient tradition requires that the bread be unleavened. The wine must be natural grape wine. Wine made from other fruit or chemically composed is not valid for the Eucharist.
Catechumens are dismissed after the Liturgy of the Word so they can continue their reflection on the word with the help of their catechists. Since catechumens are not fully initiated, they cannot receive communion.