Deductions & credits

The medical expense deduction has to meet a rather large threshold before it can affect your return. The amount of medical expenses that will count toward itemization for someone under 65 is the amount that is OVER 10% of your adjusted gross income; for someone 65 or older it would be the amount over 7.5% of your AGI.  

You should only enter the amount that you paid in 2016—do not include any amounts that were covered by insurance or that are still outstanding.  Of course, your medical expenses plus your other itemized deductions still have to exceed your standard deduction before you will see a difference in your tax due or refund.

To enter your medical expenses go to Federal>Deductions and Credits>Medical>Medical Expenses

Note:  If you are paying your Medicare premiums from your Social Security benefits, the amount taken out of your SS flows automatically to the Medical Expense section of TurboTax when you enter your SSA1099.  You do need to enter your supplemental premiums as medical expenses.  As SweetieJean mentioned, you really do not have to worry about what "category" to enter them into under Medical, as long as you enter them.  TurboTax will calculate whether you are able to get the medical expense deduction.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**