Blog / Part D

How much does Medicare Part D cost per month?

Four separate charges, only one of which is the premium. Here is what makes up your actual annual drug spending.

Updated August 17, 2026 · 3 min read

There is no single Part D price. What you pay is made of four pieces, and the monthly premium is usually the smallest of them for anyone taking regular medication.

1. The monthly premium

Set by the plan and varying widely. Low premium plans typically have narrower formularies, higher deductibles or a preferred pharmacy structure that penalizes you for filling elsewhere.

If your income is above the IRMAA threshold, you also pay a Part D surcharge. It is billed separately from your plan premium, usually deducted from Social Security, which is why people miss it. See how IRMAA works.

2. The annual deductible

The amount you pay before the plan starts sharing costs. Plans can charge up to a federal maximum, and many charge less or nothing.

A common structure applies the deductible only to higher tiers, so generics are covered from day one while brand names wait. That detail matters more than the deductible number itself. See how deductibles work in Part D.

3. Copays and coinsurance by tier

After the deductible, what you pay depends on which tier each drug sits on.

• Preferred generics, the cheapest tier
• Generics
• Preferred brand
• Non preferred drugs
• Specialty, usually coinsurance rather than a flat copay

Coinsurance is the one to watch. A percentage of a high cost specialty drug is very different from a flat copay. See how tiers work.

4. Your pharmacy

Most plans have preferred pharmacies where copays are lower and standard pharmacies where they are higher. Same plan, same drug, different price depending on where you fill it.

Mail order is often cheaper still for maintenance medications. This is worth several hundred dollars a year to some people and nothing to others.

The annual cap

Once your out of pocket spending on covered drugs reaches the annual limit, your covered prescriptions cost you nothing for the rest of the year. For anyone on expensive medication this is the number that defines the year. See the out of pocket cap.

How to work out your real cost

1. List every medication with dosage and quantity.
2. Run them through the Plan Finder at Medicare.gov with your ZIP and your pharmacy.
3. Sort by total estimated annual cost, never by premium.
4. Check the top few for prior authorization and step therapy flags.
5. Compare the winner against filling by mail order.

Getting help with the cost

Extra Help can reduce premiums, deductibles and copays substantially. The income limits are higher than most people assume, and it is widely underclaimed here. See Extra Help.

Current year figures for the deductible maximum and the out of pocket cap are set each January. Check Medicare.gov or call and we will look up the current numbers with you.