Part D is prescription drug coverage
Original Medicare (Parts A and B) does not cover prescription drugs. Many people who choose Original Medicare add a stand-alone prescription drug plan or choose a Medicare Advantage plan that includes Part D. Medicare Part D Plans are required to cover certain common types of drugs, but each plan may choose different drugs it covers. The drugs you take may not be covered by every Part D plan. You need to review each plan’s formulary (A formulary is a list of the prescription drugs that are covered by a specific Medicare Part D plan) to see if your drugs are covered. This is something I help navigate with my clients each year in the Annual Enrollment Period if needed.
Part D is optional and not everyone may need it, for example those that are eligible to get their prescriptions filled at their local VA facility or hospital. However, if you do not enroll in Part D when you first become eligible, and you decide to enroll later, you may be subject to the Part D enrollment penalty and may pay this penalty for as long as you have a prescription drug plan. The penalty is a mathematical calculation and is as follows: the number of months without a Part D drug plan × 1% × the national average price of a Medicare prescription drug plan.
In general, you may enroll in a Part D plan if you are entitled to Medicare Part A or if you are enrolled in Medicare Part B. In addition, you must live in the service area of a Part D plan you’d like to enroll in.

Explaining prescription drug coverage in 2025
Another new program for 2025!
The Medicare Prescription Payment Plan is a new program created under the Inflation Reduction Act that requires Part D plan sponsors to provide their enrollees with the option to pay out-of-pocket prescription drug costs in the form of monthly payments over the course of the plan year instead of all at once to the pharmacy. The program begins January 1, 2025. Click here to see the official CMS fact sheet with details of the plan.