Human flesh is assur. We even prohibit eating skin as a result, because it is difficult to ascertain that the piece of skin does not contain some amount of the flesh to which it was adjacent.
What you may be thinking of is human blood, which is not assur m’ikkar hadin, but it is assur because of ma’aras ayyin (since human blood looks the same as animal blood, which is assur).
n.b. the lack of an issur on consuming human blood is likely the source of the vampire legends and blood libels.