If you are claiming the Medicare premiums as a business deduction, you should not enter your Medicare premiums when entering the information from your SSA-1099, Social Security Benefits.

To get rid of the deduction showing up as a healthcare cost in addition to the business deduction, you need to revisit your Form SSA-1099 in TurboTax and delete the Medicare premium entry.  When you include it on that form, it automatically carries to Schedule A.

Please comment below if you need further assistance getting rid of the "double deduction".