Methodology: where these prices come from

What NADAC actually is

NADAC stands for National Average Drug Acquisition Cost. It's a survey-based benchmark that CMS publishes weekly, built from invoice prices that retail pharmacies report they paid to acquire drugs. It is not a sticker price. It is not what a patient pays at the register. It's closer to a snapshot of wholesale cost, averaged across reporting pharmacies for a given NDC (the 11-digit National Drug Code that identifies a specific drug, strength, and package).

CMS updates the file every week. Some NDCs move. Some don't change for months. New NDCs appear as products launch or repackage. Old ones drop off when they're no longer reported.

How we build each page

Every page on this site traces back to one weekly NADAC release. Here's the pipeline, in order:

• Collect. We pull the full NADAC file directly from CMS as soon as it's published.
• Parse. Each row in the file is one NDC with its per-unit acquisition cost and the effective date CMS assigned to that price.
• Group. Multiple NDCs often map to the same drug description (same molecule, strength, and form, different manufacturer or package size). We group those NDCs together under one drug page instead of scattering them across a dozen near-duplicate entries.
• Render. Each drug page shows the current per-unit acquisition cost, a history of how that cost has moved over past weekly files, and a list of every NDC folded into that page.

Nothing on a drug page is calculated or estimated beyond that grouping step. The number you see is the NADAC value CMS reported, tied to a specific week.

What NADAC excludes

This is the part people miss most often, so it's worth stating plainly:

• Rebates. Manufacturers pay rebates to insurers and pharmacy benefit managers after the fact. NADAC doesn't capture any of that. The acquisition cost you see is pre-rebate.
• Dispensing fees. Pharmacies charge a fee for the work of filling a prescription. That's separate from acquisition cost and not included here.
• Retail markup. What a pharmacy charges a customer, or bills an insurer, sits on top of acquisition cost. NADAC doesn't measure that markup, and this site doesn't estimate it.

Because of these gaps, NADAC is not a prediction of what anyone pays out of pocket. It's one input into that price, not the whole price. If you're comparing NADAC to a receipt or an insurance statement, expect a difference. That difference is dispensing fees, markup, insurance terms, or rebate structures, not an error in the data.

Reading the citation on each page

Every drug page on this site names the exact CMS NADAC file it pulled from and that file's effective date. If a page says a price is current, that means it matches the most recent weekly file we've processed, not a real-time feed. CMS itself doesn't update prices in real time, so nothing that cites NADAC honestly can either.

If you're checking our work, the fastest way is to look at the effective date on the page and compare it against the CMS release calendar. The number should match. If it doesn't, something on our end is stale and worth flagging.

Why this matters for how you read prices

Acquisition cost and retail price are different things measured for different purposes. This site tracks the former because it's public, it's consistent, and it's the closest thing to a paper trail on what a pharmacy actually paid to have the drug on its shelf. For more on how to read a single drug page, see how to read a drug page.