Government officials have stepped in to ban NHS Blood and Transplant from cancelling donation sessions in Dover and Folkestone.
The public body said it would halt them for two months fearing there could be post-EU chaos such as Operation Stack.
It planned to stop them for two weeks before Brexit and six weeks after - blaming potentially heavy traffic.
But the Department of Health says the idea was not approved and is being stopped.
Dover MP Charlie Elphicke earlier called the move "ridiculous" and some members of the public had told service managers to "get a grip".