Is it permissible to sign a DNR consent at any age and health status? Even for the young person. Once on life support if Drs are saying no hope, is it permissible to withdraw care?

According to Ayatollah Sistani, if one is on life support, then it cannot be withdrawn. It would be haram. Yes, you can sign a form asking them not to put you on life support, but ocne it’s put, it cannot be removed. So you should not give your consent for life support to be withdrawn.