Who may receive Communion at a Catholic Mass?
The National Conference of Bishops offers these stipulations for practicing Catholics: “In order to be properly disposed to receive Communion, participants should not be conscious of grave sin and normally should have fasted for one hour.
A person who is conscious of grave sin is not to receive the Body and Blood of the Lord without prior sacramental confession except for a grave reason where there is no opportunity for confession. In this case, the person is to be mindful of the obligation to make an act of perfect contrition, including the intentions of confessing as soon as possible (canon 916)”.
For all practical purposes, non-Catholics are excluded from taking Communion at a Catholic church. Explaining their reasoning, the National Conference of Catholic Bishops teaches that reception of the Eucharist by Christians not fully united with us would imply a oneness which does not yet exist, and for which we must all pray.