I am a senior who is self-employed and on Medicare. Can I deduct my premiums as an adjustment to gross income?

Yes. The IRS has indicated (https://www.irs.gov/pub/irs-wd/1228037.pdf) that all Medicare premiums are similar to other health insurance, and that this deduction rule extends to Medicare premiums for coverage of a self-employed individual’s spouse, dependent, or child under age 27.