Is there a way I can get a test for autism for my stepson?

His legal guardians. Have to initiate the process by first consulting the child's pediatrician. If the biological parents have joint legal custody, both must agree on non-urgent medical care of any kind, unless specific provisions in the divorce decree give one parent the sole right to make medical decisions. You can use the m-chat for screening online at firstsigns.Org, to present your concerns to his bio parents.
Mental health pro. Start with either a psychiatrist or clinical psychologist.
Yes. But it's not a simple blood test. You should start by taking the child to his primary care provider, who can then refer the child to a specialist for further evaluation if he or she thinks such a referral is warranted.