I assume you are not asking about the medicare premiums taken out of your paycheck. The following does not apply to those.
if you have a self-employment income, you can deduct your medicare premiums as self-employed health insurance. mote that the deduction is not taken on the tax form like schedule C. in desktop versions there's a link to enter self-employed health insurance. with online it should be on the page for other expenses. do report on the form for social security payments