Unfortunately, you cannot deduct medical expenses for an adult son unless he can be claimed as a dependent by you.
See the following from IRS Publication 502:
Whose Medical Expenses Can You Include?
You can generally include medical expenses you pay for yourself, as well as those you pay for someone who was your spouse or your dependent either when the services were provided or when you paid for them. There are different rules for decedents and for individuals who are the subject of multiple support agreements. See
Support claimed under a multiple support agreement
, later, under Qualifying Relative.
