Generally, Original Medicare covers most health services that are medically necessary for you.
It is a good idea to have supplemental insurance, or your out-of-pocket costs with Original Medicare can be very high. You may get supplemental insurance, for example, from an employer or a Medigap policy that works specifically with Original Medicare.
Original Medicare does not include Part D, the Medicare drug benefit. If you want Medicare Part D drug coverage, you will need to sign up for a stand-alone Part D plan, for which you must pay an additional premium.