By Christian BrinkleyLicensed NC Insurance Agent, NPN 22217190, NC Life & Health · Updated October 14, 2026 · 4 min read
Your Part D drug plan does not charge you the same amount all year. Your costs move through phases as your spending adds up. The phase you are in decides what you pay at the pharmacy counter. There are three main phases. The dollar figures that define each phase change every year, so check medicare.gov for the current year numbers. The concepts below stay the same year to year.
Phase 1: The Deductible
At the start of each year, you are in the deductible phase. During this phase, you pay the full cost of your covered drugs until you have spent enough to satisfy the plan's deductible.
Some plans have no deductible, or they waive the deductible for certain drug tiers. Many plans charge no deductible for generic drugs on the lowest tiers. Check your plan's details to see how your deductible works.
The deductible resets every January 1. Whatever you paid toward it in December does not carry over. January starts fresh.
Phase 2: Initial Coverage
Once you meet the deductible, you move into initial coverage. This is the phase most people spend most of the year in. During initial coverage, you pay a copay or coinsurance for each prescription, and your plan pays the rest.
Your costs in this phase depend on your plan's formulary. Drugs are grouped into tiers. Tier 1 generics might cost you a small copay. Tier 3 brand names cost more. Tier 5 specialty drugs usually come with coinsurance, meaning you pay a percentage of the drug's cost.
Phase 3: Catastrophic Coverage
Once your total drug costs cross the threshold, you enter catastrophic coverage. This is the final phase, and it lasts for the rest of the year.
In catastrophic coverage, your costs drop to a small amount. Medicare sets the rules for what you pay in this phase. For the current year, check medicare.gov, because the structure of catastrophic coverage has been changing under recent law.
The point of this phase is protection. It caps what you pay for drugs in a year. Without it, someone on a 10,000 dollar a month specialty drug would face ruinous costs. Catastrophic coverage is the backstop.
How the Phases Affect Real People
Most people on a few generics live in initial coverage all year. They pay their copays, the year ends, the cycle resets. The phases are background noise.
People on expensive brand or specialty drugs move through the phases quickly. Their early-year costs are high. Then catastrophic coverage kicks in and their costs drop. The yearly pattern looks like a hill: expensive at the start, cheap at the end.
If your costs spike early in the year and then fall, that is the phases working as designed. It is not a billing error.
What to Watch Each Year
Formularies change every fall. Your drug might move to a higher tier. A drug might leave the formulary entirely. The phase thresholds change too. That is why your Annual Notice of Change matters. Read it before Annual Enrollment ends.
If you take expensive drugs, ask your doctor about alternatives on lower tiers. A therapeutically similar drug on a lower tier can keep you in initial coverage longer and cut your yearly costs. Your doctor and pharmacist can help with this conversation.
The Bottom Line
Part D moves through three phases: the deductible, initial coverage, and catastrophic coverage. Your costs are highest early in the year and drop as your spending crosses each threshold. The dollar figures change yearly, so always check medicare.gov for the current year numbers before making decisions.
This article is for general information only and is not legal, tax, or insurance advice. Part D rules, thresholds, and dollar figures change every year. For free, unbiased help, contact your State Health Insurance Assistance Program (SHIP), call 1-800-MEDICARE, or talk with a local licensed insurance agent who can review your specific situation.
Questions people ask me about this
What should I know about the phases affect real people?
Most people on a few generics live in initial coverage all year. They pay their copays, the year ends, the cycle resets. The phases are background noise. People on expensive brand or specialty drugs move through the phases quickly. Their early-year costs are high. Then catastrophic coverage kicks in and their costs drop.
What to watch each year?
Formularies change every fall. Your drug might move to a higher tier. A drug might leave the formulary entirely. The phase thresholds change too. That is why your Annual Notice of Change matters. Read it before Annual Enrollment ends. If you take expensive drugs, ask your doctor about alternatives on lower tiers.
What should I know about phase 1?
At the start of each year, you are in the deductible phase. During this phase, you pay the full cost of your covered drugs until you have spent enough to satisfy the plan's deductible. Some plans have no deductible, or they waive the deductible for certain drug tiers. Many plans charge no deductible for generic drugs on the lowest tiers.
Get the next guide by email
New guides go out when they are published. No spam, no selling your address, unsubscribe any time.