Forcing someone to provide DNA or blood or blow for a BAC is like forcing someone to testify, verbal or written. It's like forcing someone to tell where they hid they body.
No. It's not. You can say that all you want but it remains untrue. It's more like taking the fingerprints and picture of someone when you arrest them, getting a description, having the victim look at them in a line-up, etc.
Being a witness and physical evidence are two entirely different things. The Constitution forbids one. It does not forbid the other.