Medicare Part D

Why the Same Pill Costs More at a Different Pharmacy

CHARLESTON, S.C. — If you've ever picked up a prescription in West Ashley and paid one price, then paid a different price for the same drug on a trip to Mount Pleasant, you're not imagining things. Under Medicare Part D, the pharmacy counter you choose can change what you owe — even when the plan, the drug, and the dose are identical. That's because every Part D plan uses a pharmacy network, and not all pharmacies in that network are treated the same.

Here's how those networks work, and how Charleston-area readers can check before they fill.

What a Part D pharmacy network actually is

Every Medicare drug plan — whether it's a stand-alone Part D plan or the drug coverage built into a Medicare Advantage plan — contracts with a group of pharmacies. That group is the plan's network. If you fill a prescription at a pharmacy inside the network, the plan helps pay. If you fill it outside the network, you may pay full price, except in limited situations like travel or emergencies.

Networks aren't small. A typical Part D plan contracts with thousands of pharmacies nationwide, including national chains, regional chains, grocery-store pharmacies, and independents. In Charleston, that usually means most of the counters you already pass on your commute are in-network for most plans — but "in-network" is only half the story.

Preferred vs. standard: same network, different price

Within a network, pharmacies are sorted into two tiers:

• Preferred pharmacies have negotiated lower cost-sharing with the plan. When you fill a covered drug there, your copay or coinsurance is generally lower.
• Standard pharmacies are still in-network and still covered, but the cost-sharing tends to be higher for the same drug.

That's why the same 30-day supply of the same medication can ring up at two different amounts across town. Nothing is wrong with the pharmacy or the plan — you're just paying the tier the plan assigned to that counter.

The catch: preferred status is set by each plan individually. A pharmacy that's preferred under one plan may be standard — or not in the network at all — under another. It can also change from year to year, which is one reason CMS encourages beneficiaries to re-check their coverage each fall during the Annual Enrollment Period (Oct. 15 – Dec. 7).

Where mail order fits in

Most Part D plans also contract with a mail-order pharmacy. Mail order is typically built for maintenance medications — the ones you take every day for blood pressure, cholesterol, diabetes, and similar long-term conditions — and it often ships a 90-day supply at a time.

For some drugs and some plans, mail order carries lower cost-sharing than a retail counter. For others, a 90-day fill at a preferred retail pharmacy costs about the same. And for controlled substances or drugs that need refrigeration, mail order may not be an option at all. The only way to know which route is cheaper for your specific list is to compare them side by side.

How to check before you fill

The Charleston area sits in Charleston County, where residents have a wide field of stand-alone Part D and Medicare Advantage drug plans to choose from — enough that the differences in pharmacy networks matter. Before you enroll, switch, or even refill, it's worth doing this quick check:

1. Go to Medicare.gov/plan-compare and log in (or start as a guest). 2. Enter your ZIP code and your full drug list, including doses. 3. Add the pharmacies you actually use — for example, one near home in North Charleston and one near work downtown. 4. Add "mail order" as an option so the tool prices it too. 5. Look at the total yearly drug cost each plan shows for each pharmacy. That's where preferred vs. standard vs. mail order shows up in plain dollars.

If the online tool feels like a lot, call 1-800-MEDICARE (1-800-633-4227), available 24/7, or contact South Carolina SHIP (Insurance Counseling Assistance and Referrals for Elders) at 1-800-868-9095. SHIP counselors are trained, free, and don't sell plans.

A few 2027 numbers worth knowing

Pharmacy tier can shift what you pay per fill, but two program-wide guardrails apply no matter which counter you use:

• The annual out-of-pocket cap is $2,100 in 2026 and $2,400 in 2027. Once your covered drug spending hits that ceiling, you pay nothing for covered Part D drugs the rest of the year.
• The maximum Part D deductible is $615 in 2026 and $700 in 2027. Plans can set a lower deductible, but not higher.
• If a large fill early in the year is hard to handle, the Medicare Prescription Payment Plan lets you spread Part D costs across the calendar year in monthly installments instead of paying all at once at the counter.