> ## Documentation Index
> Fetch the complete documentation index at: https://docs.omophub.com/llms.txt
> Use this file to discover all available pages before exploring further.

# CPT4 access

> Validate UMLS access in the Dashboard, understand annual renewal, and use CPT4 safely across OMOPHub APIs.

OMOPHub makes CPT4 content available only to an authenticated user who has
completed the annual UMLS validation flow. An OMOPHub API key by itself does
not grant CPT4 access.

## Validate your access

1. Create or renew your UMLS account and accept the current terms at the
   [UMLS Terminology Services](https://uts.nlm.nih.gov/uts/).
2. Copy your API key from your [UTS profile](https://uts.nlm.nih.gov/uts/profile).
3. Sign in to the OMOPHub Dashboard, open **Settings → Vocabulary access**, and
   submit the key under **CPT4**.
4. Wait for the **Verified** status before calling the API.

OMOPHub sends the submitted key directly to NLM for validation. It does not
store the key, include it in application logs, or return it to the browser.
Only the validation result and its expiry date are retained in the audit trail.

## Expiration and API keys

A successful validation applies to every active OMOPHub API key owned by the
same Dashboard user. It remains valid until **January 30 at 00:00 UTC of the
next calendar year**. Revalidate in the Dashboard after that boundary; an
expired grant fails closed until validation succeeds again.

## Supported surfaces

Validated users can use CPT4 through direct REST lookup, text and semantic
search, mappings, relationships, hierarchy operations, statistics, the FHIR
Concept Resolver, and the FHIR Terminology Service.

Unvalidated or expired users receive HTTP `403` with the stable REST error code
`vocabulary_restricted`. FHIR terminology operations return the corresponding
`OperationOutcome`. Numeric concept-ID probes remain intentionally opaque and
may return `404` where revealing the vocabulary would disclose restricted data.

## Licensing notice

CPT® is a registered trademark of the American Medical Association. CPT
content is copyright American Medical Association. All rights reserved.

UMLS validation confirms access to the NLM service; it does not transfer AMA
rights or replace your organization's responsibility to obtain and follow any
required CPT license. See the [AMA CPT licensing FAQ](https://www.ama-assn.org/practice-management/cpt/cpt-licensing-frequently-asked-questions-faqs)
and the [NLM UMLS license information](https://www.nlm.nih.gov/databases/umls.html).

For error handling details, see [API error codes](/api-reference/errors#licence-restricted-vocabularies).