Yes, the Medicare portion is automatically carried to Schedule A, so you do not need to enter it yourself. You will need to enter the supplemental and prescription costs.
Yes, If you itemize your deduction, the premiums can be tax deductible even if they're deducted automatically from your Social Security benefits. Also the Medicare supplement and Medicare Part D that you pay out of pocket can be deductible. However, you may deduct only the amount of your total unreimbursed medical expenses that exceed 7.5 percent of your adjusted gross income
My social security SSA-1099 deducts Medicare Part B premium from my SS income but since I pay my supplemental and prescription coverage Part D myself they are not deducted. If SS paid these two premiums I assume they would be deducted from SS income instead of adding them to Schedule A which is meaning less for most people since their itemized deductions do not exceed the Standard deduction. Can I deduct these two premiums from my Social Security income?
No. Medical premiums paid are potential itemized deductions as medical expenses. While the medicare premiums Part B are withheld/deducted from the social security pay you actually received, they are still part of the benefits included in box 5.
Therefore any medicare premiums withheld are automatically entered as medical expenses in TurboTax. If you pay Part D and/or supplemental premiums out-of-pocket those too are potential itemized deductions, however, you must actually enter those amounts in the "Medical Expenses" topic.
Any medical expenses that exceed 7.5% of your adjusted gross income will be included in itemized deductions. If your itemized deductions exceed your standard deduction, itemized deductions will be selected/recommended by TurboTax.