Unless something has changed I don't think the United States Supreme Court has made any rulings on mature minors regarding the blood issue.

But for children in general in 1979: “The law’s concept of the family rests on a presumption that parents possess what a child lacks in maturity, experience, and capacity for judgment required for making life’s difficult decisions. . . . Simply because the decision of a parent [on a medical matter] involves risks does not automatically transfer the power to make that decision from the parents to some agency or officer of the state.”—Parham v. J.R.

That is the only one that I know of.