Catholics who have received sufficent formation and celebrated their First Communion must meet conditions to continue receiving Communion. They are as follows:
1. Be in a state of grace, meaning no mortal sins on your soul.
2. Must believe that the Eucharist is truly Jesus' body, blood, soul and divinity.
3. Must observe the Eucharistic fast, meaning no food or drink (except water) for an hour before receiving.
4. Must not be must not be under an ecclesiastical censure.
Scripture is clear that partaking of the Eucharist is among the highest signs of Christian unity: "Because there is one bread, we who are many are one body, for we all partake of the one bread" (1 Cor. 10:17). For this reason, it is normally impossible for non-Catholic Christians to receive Holy Communion, for to do so would be to proclaim a unity to exist that, regrettably, does not.
Another reason that many non-Catholics may not ordinarily receive Communion is for their own protection, since many reject the doctrine of the Real Presence of Christ in the Eucharist. Scripture warns that it is very dangerous for one not believing in the Real Presence to receive Communion: "For any one who eats and drinks without discerning the body eats and drinks judgment upon himself. That is why many of you are weak and ill, and some have died" (1 Cor. 11:29–30).