How do I determine Medicare B Premiums Deducted From Your Benefit?

Look at your 1099-SSA. On the left of the form, there will be a box titled: DESCRIPTION OF AMOUNT IN BOX 3. In this box is where you will find any Medicare premiums deducted. 

But how do I know if it is for part B, C or D and how much.  It just says the deduction form your benefits for medicare.

Medicare Part B and d are both labeled as Part B or D on your SSA-1099 on the left side. 

Medicare Part C doesn't show up on your SSA-1099 at all. If you are paying out of pocket for Medicare Part C, you will need to get the amount from your records.