IRS Publication 502 Medical and Dental Expenses page 3 - https://www.irs.gov/pub/irs-pdf/p502.pdf#page=3
You can include medical expenses you paid for an individual that would have been your dependent except that:
1. He or she received gross income of $4,300 or more in 2021;
2. He or she filed a joint return for 2021;
