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Payment Limit API

Medicare Part B payment limits and ASP by HCPCS procedure code, version 1.

Base URL

https://www.medpharmdata.com/api/v1/

Authentication

Every request needs a key. Send it in either header — use whichever your HTTP client makes easier:

X-API-Key: mpd_live_xxxxxxxx
Authorization: Bearer mpd_live_xxxxxxxx

Keys are issued by MedPharmData and shown once. We store only a hash, so a lost key cannot be recovered — ask for a replacement and the old one will be revoked. Treat it like a password: it identifies your organisation, not an individual user.

Look up one code

GET https://www.medpharmdata.com/api/v1/payment-limits/J1745/

{
  "hcpcs_code": "J1745",
  "description": "Injection, infliximab, excluding biosimilar, 10 mg",
  "dosage": "10 MG",
  "current": {
    "quarter": "2026Q3",
    "year": 2026,
    "quarter_number": 3,
    "payment_limit": "82.510",
    "asp": "77.839623",
    "asp_source": "derived_asp_plus_6",
    "coinsurance_percent": 20,
    "notes": null,
    "source_file": "July 2026 Medicare Part B Payment Limit File 061626.xls"
  }
}

An unknown code returns 404 with an explanation, rather than an empty success — so your error handling can tell "no such price" apart from "lookup worked, found nothing".

Look up many at once

GET https://www.medpharmdata.com/api/v1/payment-limits/?codes=J1745,J9035,J0135

Up to 100 codes per request. The response lists any codes with no pricing under not_found, so you do not have to diff your request against the reply:

{
  "count": 2,
  "not_found": ["J0135"],
  "results": [ ... ]
}

Parameters

Parameter	Effect
`quarter`	Pin a period, e.g. `quarter=2026Q3`. Defaults to the most recent loaded quarter. Use this to reproduce a calculation exactly as it stood at the time. Valid values come from `https://www.medpharmdata.com/api/v1/quarters/`.
`history`	`history=true` adds a `history` array with every loaded quarter, newest first, alongside `current`.
`codes`	Comma-separated list, batch endpoint only. Duplicates are collapsed; your ordering is preserved.

How to read the numbers

Amounts are strings, not JSON numbers. A payment limit is an exact decimal; parsing it as a float would introduce rounding into a figure you reconcile against CMS to the cent. Parse it into your language's decimal type.

Every asp we return is an estimate, not a CMS figure. CMS does not publish ASP in the payment limit file at all. We compute it by removing the statutory 6% markup. If you need an official ASP, the payment limit is the published number — the ASP is ours.

Biosimilars do not use the same formula. Medicare pays a biosimilar its own ASP plus an add-on based on the reference product's ASP, so dividing a biosimilar payment limit by 1.06 overstates the ASP by the whole add-on. We compute those separately and tell you which basis was used.

derived_asp_plus_6 — payment_limit ÷ 1.06.
derived_biosimilar_reference — payment_limit − (reference_asp × reference_addon_percent). The response includes reference_hcpcs_code, reference_asp and reference_addon_percent so you can reproduce it.
unavailable_biosimilar_reference_missing — asp is null. It is a biosimilar, but we have no reference product recorded, so the calculation cannot be completed. The payment limit is still correct and still usable.
unavailable — asp is null. The code is a vaccine, blood product or clotting factor, or its notes show the limit was set from WAC, AWP or by a contractor. Dividing those by 1.06 would produce a number that looks like an ASP and is not one, so we return nothing rather than mislead. Treat null as "unknown", never as zero.

Available quarters

GET https://www.medpharmdata.com/api/v1/quarters/

New CMS releases are loaded weekly. Data appears here as soon as it loads; there is no separate publication step.

Limits and errors

Status	Meaning
`400`	Malformed code, or more than 100 codes.
`401`	Key missing, unknown or revoked.
`404`	Valid code, but no payment limit for it in the requested period.
`429`	Rate limit exceeded. `Retry-After` says how long to wait.

The default limit is 1000 requests per hour per key. Batch requests count as one. If you need more, ask — limits are set per key.

Example

curl -H "X-API-Key: $MPD_API_KEY" \
  "https://www.medpharmdata.com/api/v1/payment-limits/?codes=J1745,J9035"

Prefer to ask in plain language?

MedPharmData is also an MCP server, so Claude can answer pricing questions directly — "what does Medicare pay for infliximab?" — without you writing any code against this API.

MCP server documentation

Source data is published by CMS. MedPharmData loads it and derives ASP as described above; we do not alter published payment limits. Questions or a key request: get in touch.