Much to my own surprise, they are not quite the same thing.
The doctrine of *consubstantiation *does not teach that the substance of the bread and wine disappear or are replaced, but rather that they exist alongside the substance of the Lord.
Luther’s “sacramental union” is, in a way, very similar, however there are slight differences. For instance, it does not assert a “local” (three dimensional, circumscribed) presence of the body and blood in the sacramental bread and wine respectively, which is rejected as “gross, carnal, and Capernaitic” in the Formula of Concord (

).
The Lutheran scholar Gene Veith wrote in his
blog:
While all of these are, of course, just distortions of the Church teachings on the Eucharist, they still acknowledge the basic fact that the Blessed Sacrament is the true Body and Blood of the Lord.
However, once you start distorting Sacred Tradition, there is no stopping, and it was a matter of time for some protestant communities to actually develop the teaching that the Eucharist is nothing but bread and wine (which, of course, is the truth in the absence of valid consecration :sad_yes