Parents of special needs children are often under the assumption that they will still be able to make parental decisions for their children even after their children legally become adults. However, generally speaking, any child who reaches the age of majority, including a child with special needs, becomes an adult under the law and is entitled to all the rights and privileges of citizenship. In fact, in many states, a certain number of those rights, including the right to seek medical care without a parent’s permission, attach well before a child legally becomes an adult. So, just being the parent of a child with special needs does not automatically give you the right to make decisions for your child when they become an adult. You will need to file for guardianship.
You can file for guardianship in your child’s early teenage years if you want to be sure that you are able to control all medical decisions with regards to your child and have access to their medical records (this is typically the first kind of guardianship that is sought, and is a limited guardianship because it has a very narrow scope of application). Later, you can file for other forms of guardianship, whether a limited or full guardianship, depending on the extent of your child’s need and capacity. Like other guardianships, the court will grant only as much guardianship as is necessary for the best interests of the special needs individual, meaning that if your child has the capacity to make certain decisions for themselves, the court will not restrict those rights.
Having guardianship does not place you at odds with your child, but puts you in a position to protect them and make decisions with regards to their life and care when they are unable to competently make those decisions for themselves.