Yes, premiums for Medicare supplemental insurance and prescription insurance are deductible, if they were paid for with after-tax dollars (usually are). Also out-of-pocket prescription expenses are deductible (since "out of pocket" usually means after-tax).

However, note that to actually affect your tax return, only the medical expenses that exceed 7.5% of your adjusted gross income (AGI) are reported on Schedule A (Itemized Deductions). And if your Itemized Deductions are less than your Standard Deductions, TurboTax will take the Standard Deduction anyway.

But until you enter all your deductions, you won't know, so go ahead and enter the items under Federal->Deductions & Credits->Medical.