Do I need a witness or notary to my Michigan living will?

You will need witnesses to sign your living will in the state of Michigan. If you take a look at the following example of a Michigan living will in pdf format, you will see spaces for witnesses to sign near the bottom of the document. http://www.halt.org/living_wills/michigan.pdf

In order for the living will to be legally binding it must be witnessed and notarized. This makes it much harder for your heirs to contest the will and claim it's illegitimate.