Receiving the Eucharist while in a state of mortal sin is another mortal sin and should be confessed.
One’s culpability would be mitigated if one did not know that it was offensive to God, but it would still be a good idea to confess it. If one does know that receiving the Eucharist in a state of mortal sin is a mortal sin and does it anyway, then one would have to ask… why receive the Eucharist?