Mustum and wine only
Receiving the Precious Blood alone is full sacramental Communion. Here is how it works at Mass, and how to discuss mustum with your pastor when alcohol is also a concern.
The whole Christ under either species
The Church teaches that Christ is wholly present under either the consecrated bread or the consecrated wine. A Catholic who cannot receive a host may receive the Precious Blood alone, even when the chalice is not offered to the rest of the congregation. See the USCCB’s pastoral guidance.
The particle in the chalice
During the fraction rite the priest breaks the large host and drops a particle of it into the chalice. The amount of wheat is minute, and people with celiac disease receive from the ordinary chalice every day without trouble. Drink from the common cup. You do not need a separate chalice prepared for you.
Handling and previous drinkers can also introduce gluten. Agree on the preparation and distribution before Mass. Celiac disease may cause complications without noticeable symptoms, so symptoms are not a reliable way to judge an exposure.
What mustum is
The Vatican’s 2017 letter, paragraph 4, defines mustum as grape juice that is fresh or preserved by a method that suspends fermentation without changing its nature, such as freezing. It is valid matter for the Eucharist when those conditions are met.
Mustum can contain a small amount of alcohol. If alcohol is a medical concern, discuss the specific preparation with your clinician and your pastor. Your parish should confirm that the mustum meets the Church’s requirements and follow its storage instructions.
Permission
The competent Ordinary may grant permission to use mustum or low-gluten hosts, including ongoing permission while the need continues. In the United States, the diocesan bishop may delegate permission for laypeople to pastors. The USCCB states that medical certification is not required. Begin with your parish, which can explain the diocesan process.
At Mass
A chalice of mustum can be prepared for the priest to consecrate during Mass. Only a validly ordained priest can consecrate the Eucharist; distribution may be entrusted to an authorized minister of Holy Communion. These roles are distinguished in canons 900 and 910.
Before Mass, agree on the mustum and where and from whom you will receive. The parish conversation card can help you prepare.