Medicare Part D: Prescription Drug Plans Made Clear

Part D is Medicare's prescription drug coverage. It is offered through private insurance plans that follow rules set by Medicare. Original Medicare (Parts A and B) does not cover most medications you take at home — that is the gap Part D fills.

Part D is voluntary, but waiting can have a cost. If you go without creditable drug coverage after becoming eligible, a late-enrollment penalty builds for each month you wait and is added to your premium when you do enroll. That is why it is worth deciding on drug coverage when you first get Medicare, even if you take few medications today.

There are two paths, and which one fits you depends on how you get the rest of your Medicare.

A formulary is simply the plan's list of covered drugs. If a medication is not on the list, the plan generally does not pay for it. Every plan's list is different, which is why the same medication can be covered by one plan and not by another.

Drugs on the list are grouped into tiers — cost levels. Lower tiers usually mean a lower copay, and generic drugs usually sit in lower tiers than brand-name drugs. Some drugs also carry rules such as prior authorization (plan approval before filling) or quantity limits.

Plans change their drug lists, tiers, and pharmacy networks every year. A plan that fit you well last year may cover your medications differently next year — even if you change nothing. The plan mails a notice of changes each fall, but many people never read it.

Since getting licensed in 2019, Rachel has kept one simple rule: trust the current-year documents, not last year's memory. Each fall she can recheck your medication list against your plan's new list, so nothing surprises you at the pharmacy in January.

If you go without Part D or other creditable drug coverage — coverage at least as good as Medicare's standard, such as many employer plans — a penalty accrues for every month you wait. When you later enroll, that penalty is added to your monthly premium. The amount depends on how long you waited and changes each year, so there is no single number to quote.

The good news: enrolling on time, or keeping creditable coverage, avoids the penalty entirely. If you are not sure whether your current coverage counts as creditable, ask before you drop anything — it is a five-minute question.

Extra Help — also called the Low-Income Subsidy (LIS) — is a federal program that lowers prescription costs for people with limited income and resources. Many people qualify without knowing it, so it is always worth asking.

Seniors who have both Medicare and Medi-Cal (called 'dual eligible') may qualify for Extra Help as well, and special plans exist for people with both programs. Rachel helps Korean-American seniors across Los Angeles and Orange County sort out how Medicare, Medi-Cal, and Extra Help fit together — in plain Korean or English, without the paperwork headache.