How often these prices update

Where the numbers come from

Every price you see on RxTrueCost traces back to the NADAC file: National Average Drug Acquisition Cost. CMS builds this from a survey of pharmacy invoices, not from wholesaler price lists or list prices. It's an estimate of what pharmacies actually paid to acquire a drug, averaged across many purchases.

CMS runs this survey on an ongoing basis and publishes updated files. Two update rhythms matter here.

Weekly files and the monthly survey refresh

CMS releases a NADAC file most weeks. These weekly releases mostly reflect small adjustments: new drugs entering the file, price changes for products where new invoice data came in, or corrections.

Once a month, CMS does a fuller survey refresh. This is when the broader base of pharmacy invoice data gets reprocessed and more prices move at once. If you notice a bigger jump or a batch of drugs changing on the same week, that's usually the monthly refresh showing up rather than a weekly tweak.

Each row in the file carries an effective date. That date tells you when CMS considers that acquisition cost estimate valid, not the date the file happened to land in our system. We display that effective date next to every price so you know exactly which CMS release it came from.

Why a page's number can lag a market move

A few things cause the number on a given drug page to trail what's happening in the market right now:

• Survey timing. NADAC reflects invoices pharmacies already paid. If a manufacturer changes price today, that change has to show up in pharmacy purchasing first, then in the survey data, then in a published file. That chain takes time.
• Weekly vs. monthly cadence. A drug that only gets touched during the monthly refresh won't show a new number until that refresh happens, even if the market moved weeks earlier.
• Sparse data for some drugs. CMS needs enough invoice volume to calculate a reliable average. Low-volume drugs sometimes go longer between meaningful updates.
• Acquisition cost isn't retail price. NADAC estimates what a pharmacy pays to acquire a drug. It's not what a pharmacy charges a customer at the counter, and it's not a list price. These two numbers move independently, which is part of why NADAC can look "behind" a retail price change that already hit the news.

None of this means the data is wrong. It means you're looking at a snapshot with a known effective date, built from a survey process that has its own pace.

How our collector picks up each file

Our collector checks for a new CMS NADAC file on a regular schedule. When a new file publishes, we pull it, match it against the prior week's data, and update prices where the file shows a change. We keep the CMS effective date attached to every number, so what you see is traceable back to a specific release.

We don't smooth, average across weeks, or estimate ahead of what CMS publishes. If CMS hasn't updated a drug, we don't either. That's a deliberate choice: better to show you the most recent real file than to guess at where a price might be heading.

Reading a price page with this in mind

When you check a number here, look at the effective date first. That tells you how current the estimate is. If a drug hasn't moved in a while, that's often just quiet survey data, not a stale page. For background on the underlying source, see what NADAC actually measures.