Cartos – ONC’s Terminology Service User Guide
This guide explains how to access, find, and use terminology content and services available through Cartos.
Overview
Cartos is an Health Level Seven HL7® Fast Health Interoperability Resources FHIR® -enabled terminology service that centralizes access to value sets, code systems, and terminology collections aligned with the Office of the National Coordinator for Health Information Technology (ONC) regulations, the ONC Health IT Certification Program, and the ONC Standards Version Advancement Process (SVAP).
Access is available via an application programming interface (API) or an interactive web browser built for discovering terminology assets and the relationships between them.
While Cartos delivers comprehensive terminology services, it is not the single source for every healthcare terminology.
- For code systems with established distribution mechanisms, such as RxNorm, Cartos provides metadata and a trusted reference to the authoritative source in the Unified Medical Language System.
- For proprietary content such as CPT®, Cartos directs users to the authoritative publisher rather than creating an additional licensing or redistribution process.
This approach supports efficient access to the most current, authoritative terminology resources while respecting publisher licensing requirements.
Why Cartos? – Terminology management simplified
Today, implementers must gather terminology assets from multiple sources such as implementation guides, web sites, and terminology servers. It is not unusual to find duplicate or inconsistent versions of the same asset across multiple locations. This results in users spending an unreasonable amount of time to find the content they need.
This is where Cartos comes in. It brings regulatory context, implementation guide references, terminology metadata, and terminology content together in a single, authoritative location. Users can access the content they need via browser-based search, a standards-based FHIR R4 API, or downloadable terminology collections, depending on what works best for their workflow.
Implementers find what they need faster, confirm they are working from the correct, current terminology version, and eliminate duplicative research.
More consistent terminology use across health IT products and public health programs is central to ONC’s interoperability mission. Cartos supports this by giving implementers nationwide a single, reliable source for the terminology content their systems depend on.
How to Access Cartos
Cartos offers three ways to find and use terminology content:
- FHIR API: Connect your software directly to Cartos using the standard FHIR R4-compliant API. Built for developers who need to search, validate, and retrieve terminology content programmatically. A Swagger page is also available for testing.
- Terminology Web Browser (Cartos Terminology Browser): Search and browse terminology content without technical setup required. Users can find code systems and value sets by name, or search by regulation. Access to Cartos Terminology Browser is open.
- Content bundles (on HealthIT.gov): Download terminology content organized by implementation guide or SVAP (e.g., US Core). This is useful if you want all value set expansions for an implementation guide, without searching for each one.
Cartos FHIR API
Overview
Cartos provides a read-only application programming interface (API) built on the HL7 FHIR R4 standard. The API is intended for terminology discovery, design-time queries and validation, research, and periodic retrieval of terminology content. Production clinical applications must not rely on the Cartos API for direct runtime terminology queries. Organizations supporting production workflows should deploy or procure a local terminology service. Read-only means that you cannot create, edit, or delete content via the API.
Who Uses the API?
The API is for health IT developers and integration engineers who build and/or maintain health IT systems. Users may also be public health agencies, researchers, and teams that automate terminology validation in data pipelines. Users can leverage the API to support standards-based terminology lookup, value set expansion, concept code validation, and integration of authoritative terminology content into health IT workflows.
If you prefer to search for content online instead of connecting software to the API or the Swagger page, use the Cartos Terminology Browser.
What Can You Do with the API?
- Retrieve value sets and code systems
- Expand a value set to see the member concepts
- Look up a specific concept code to get its definition and properties
- Validate whether a concept code is valid within a given code system or value set
- Compare concept codes to check the parent-child or category-subcategory link between them
- Search for terminology resources by name, identifier, canonical URL, or other parameters
FHIR R4 Conformance
The Cartos API conforms to the HL7 FHIR R4 specification for terminology services. This means that all supported resources and operations follow FHIR R4 data models and interaction patterns. A CapabilityStatement is exposed and describes exactly what the API supports, responses use standard FHIR resource formats in JSON, and error responses use the FHIR OperationOutcome resource. Additionally, a TerminologyCapabilities resource provides information about the code systems the service supports.
How to Access the API
The Cartos API is publicly available and can be accessed via this base URL: https://cartos.healthit.gov/TerminologyServer/R4.
Rate Limits and Fair Use
The Cartos API is a public resource. The following rate limits are in place to ensure that the public service remains stable for all users.
| Limit | Value |
|---|---|
| Requests per 5-minute window (per IP address) | 2,000 |
| Default value set expansion count (per page) | 2,000 |
| Maximum value set expansion count (per page) | 2,000 |
Note: The 2,000-term limit applies per page, not to the total concept count in a value set expansion. Value set expansions containing more than 2,000 concepts are paginated, not truncated. To retrieve the full expansion of a large value set, make subsequent API calls using the pagination parameters returned in the response until all pages have been retrieved.
If you exceed the rate limit, the API will return an HTTP 429 Too Many Requests response. The response will include a Retry-After header indicating how long to wait before retrying.
In the unlikely situation where your use case requires higher limits, submit a request to the ONC Cartos team for consideration. Do not use automated scripts to work around rate limits.
Supported Resources – Read and Search
The Cartos API supports the following FHIR terminology resources in read and search mode.
CodeSystem
Per FHIR 4.0.1 – The CodeSystem resource is used to declare the existence of and describe a code system or code system supplement and its key properties and optionally define a part or all of its content.
| Interaction | Description | Example |
|---|---|---|
| GET [base]/CodeSystem | Retrieve list of all supported code systems | GET [base]/CodeSystem |
| GET [base]/CodeSystem?[parameters] | Find code systems using standard FHIR search parameters | GET [base]/CodeSystem?url=http://loinc.org |
ValueSet
Per FHIR 4.0.1 – A ValueSet resource instance specifies a set of concept codes drawn from one or more code systems, intended for use in a particular context.
When proprietary content is referenced, ValueSet.description contains available metadata and guidance about where users can obtain the proprietary terminology content. Cartos does not host, redistribute, or display proprietary concept codes. Users must obtain access to proprietary terminology content directly from the authoritative publisher.
| Interaction | Description | Example |
|---|---|---|
| GET [base]/ValueSet/ | Retrieve list of all supported value sets | GET [base]/ValueSet |
| GET [base]/ValueSet?[parameters] | Search for value sets using standard FHIR search parameters | GET [base]/ValueSet?name=smoking&status=active |
Terminology Operations
In addition to retrieving resources, the Cartos API supports the following FHIR terminology operations.
$expand
Use this operation to return the list of concept codes in a value set expansion. Expansions are limited to 2,000 concept codes per page. To retrieve the full expansion of a large value set, make subsequent API calls using the pagination parameters returned in the response until all pages have been retrieved.
Note that ValueSet resources containing concept codes from proprietary code systems will be returned with ValueSet.description valued with available metadata and guidance about where users can obtain the proprietary terminology. Proprietary content will not be reflected in the value set expansions due to licensing restrictions.
GET [base]/ValueSet/[id]/$expand
GET [base]/ValueSet/$expand?url=[canonical-url]
Input Parameters
The table below represents a subset of supported input parameters. Combine parameters if you wish to further narrow your search results.
| Parameter | Description | Example |
|---|---|---|
| url | The canonical URL of the value set | http://cts.nlm.nih.gov/fhir/ValueSet/ 2.16.840.1.113762.1.4.1146.839 |
| valueSetVersion | The specific version of the value set | 20230122 |
| filter | Limit expansion results to concepts matching a text string | mycobacterium |
| count | Number of concepts to return per page | 50 |
| offset | Starting point for paged results | 0 |
| activeOnly | Controls whether inactive concepts are included or excluded in value set expansions | true |
| Example: GET [base]/ValueSet/$expand?url= http://cts.nlm.nih.gov/fhir/ValueSet/ 2.16.840.1.113762.1.4.1146.839&valueSetVersion=20230122 | ||
$lookup
Use this operation to return detailed information about a concept code within a code system, including its display name, definition, and properties.
For proprietary code systems, a $lookup request in Cartos will return a not found error because the underlying proprietary terminology content is not available for lookup due to licensing restrictions.
Operation Definition: $lookup
GET [base]/CodeSystem/$lookup?system=[system-url]&code=[code]
Input Parameters
The table below represents a subset of supported input parameters. When invoking this operation, users must provide both a system and a code, either using the system and code parameters, or in the coding parameter. Other parameters are optional.
| Parameter | Description | Example |
|---|---|---|
| system | The canonical URL of the code system | http://hl7.org/fhir/us/core/CodeSystem/us-core-category |
| code | The concept code you want to look up | cognitive-status |
| coding | A JSON-formatted tuple of system and code | {“system”:” http://hl7.org/fhir/us/core/CodeSystem/us-core-category”, “code”:”cognitive-status”} |
| version | The version of the code system to search in | 6.1.0 |
| property | A list of properties to return. If empty, the server default is to return all available properties. | display |
| Example: GET [base]/CodeSystem/$lookup?system=http://hl7.org/fhir/us/core/CodeSystem/us-core-category &code=cognitive-status&version=6.1.0 | ||
$validate-code
Use this operation to check if a given concept code is valid within a code system or value set.
For proprietary code systems, a $validate-code request in Cartos will return a not found error because the underlying proprietary terminology content is not available for lookup due to licensing restrictions.
Operation Definition: $validate-code on CodeSystem
GET [base]/CodeSystem/$validate-code?url=[system-url]&code=[code]
Operation Definition: $validate-code in ValueSet
GET [base]/ValueSet/$validate-code?url=[valueset-url]&code=[code]&system=[system-url]
Input Parameters
The table below represents a subset of supported input parameters.
| Parameter | Description | |
|---|---|---|
| url | The canonical URL of the code system or value set | |
| code | The code to validate | |
| system | The code system the value set’s expansion concept code comes from (only used in ValueSet $validate-code) | |
| display | The display name to validate alongside the code | |
| coding | A JSON-formatted tuple of system and code | |
| codeableConcept | A JSON-formatted FHIR codeable concept object. [Object specifications] | |
| version | The version to validate against | |
| CodeSystem Example: GET [base]/CodeSystem/$validate-code?url=http://www.nlm.nih.gov/research/umls/rxnorm&code=1486972 | ||
| ValueSet Example: GET [base]/ValueSet/$validate-code?url=http://cts.nlm.nih.gov/fhir/ValueSet/2.16.840.1.113762.1.4.1021.30&system=http://ncicb.nci.nih.gov/xml/owl/EVS/Thesaurus.owl&code=C44278 | ||
$subsumes
Use this operation to check if two concepts have a subsumption (hierarchically-encompassing) relationship based on their underlying code system.
Operation Definition: $subsumes on CodeSystem
GET [base]/CodeSystem/$subsumes?codeA=[concept code A]&codeB=[concept code B]&system=[code system]
Input Parameters
| Parameter | Description | |
|---|---|---|
| codeA | The canonical URL of the code system or value set | |
| codeB | The code to validate | |
| system | The code system the value set’s expansion concept code comes from (only used in ValueSet $validate-code) | |
| version | The display name to validate alongside the code | |
| codingA | A JSON-formatted tuple of system and code | |
| codingB | A JSON-formatted FHIR codeable concept object. [Object specifications] | |
| Example: GET[base]/CodeSystem/$subsumes?codeA=3738000&codeB=235856003&system= http://snomed.info/sct | ||
Error Handling
A valid request and expected response will result in an HTTP 200, OK Operational Outcome status. When the server gets an invalid request and/or the response is not successful, the API returns a standard FHIR OperationOutcome resource describing the problem. The supported status codes are summarized below.
HTTP Status Codes
| Code | Meaning |
|---|---|
| 200 OK | The request succeeded |
| 400 Bad Request | The request was malformed or missing required parameters |
| 404 Not Found | The requested resource does not exist on the server |
| 429 Too Many Requests | Rate limit exceeded |
| 500 Internal Server Error | An unexpected server error occurred; contact support if this persists |
Common Errors and How to Resolve
| Error | Likely Cause | Recommendation |
|---|---|---|
| 400 on $expand | Missing url or parameter | Check that you have included a valid value set URL or identifier |
| 404 on a resource | The resource does not exist on the Cartos server | Verify the canonical URL or ID |
| 400 on $lookup and $subsumes | The concept code does not exist in the specified resource | Check the code and system URL; confirm you are querying the right version |
| 429 | Too many requests in a short window | Review rate limits and fair use |
Change Log and Versioning
The Cartos API follows a versioned release model. Any planned breaking change will be announced on HealthIT.gov in advance.
What counts as a breaking change:
- Removing a supported resource type or operation
- Changing the structure of a response in a way that would break existing integrations
- Removing a supported search parameter
What does not count as a breaking change:
- Adding new optional parameters
- Adding new elements to a response
- Publishing new content (e.g., new code systems or value sets and new versions of code systems or value sets)
Cartos Terminology Browser (ONC Terminology Browser)
Overview
ONC Terminology Browser is the web-based search tool for Cartos. You can browse and search for terminology content directly in your web browser. No log in or account set up is required.
ONC Terminology Browser provides the following features:
- Find a code system: Review its available version, content steward, and implementation guides that reference that code system.
A code system is the source terminology that concept codes and terms come from. (Examples include SNOMED CT® US Edition and LOINC®)
- Find a value set: Review the concept codes in the expansion, available version(s), content steward, and implementation guides where the value set is referenced.
A value set is a curated list of concepts from one or more code systems, used for a specific purpose. (Examples include US Core Condition Codes and Laboratory Test Result Value Set)
- Connect terminology to regulations: Find the value sets and code systems required for a certification criterion or find the implementation guides that reference a value set or code system.
How to Browse and Search
The Cartos Terminology Browser provides a user-friendly interface for searching and browsing code systems, value sets, and terminology collections available within Cartos.
When you open the Home page, you will see a search bar at the top left with a dropdown to narrow your search and/or browse the following:
- Code Systems – find a code system by name
- Value Sets – find a value set by name
- Collections – find the value sets and code systems referenced by a specific regulation criterion, SVAP, or implementation guide
You can switch among these options on the same page.
Code Systems
To search for a code system, select the Code Systems option from the search drop down menu, and enter the name or portion of the name of the code system you are looking for in the search box (for example, “LOINC” or “CDC Race and Ethnicity”). If you prefer to browse all the code systems in Cartos, click the search icon to perform an open search and the entire list of code systems will display.
Double click on the code system name to see information about the code system version, steward and identifiers. You will also be able to see all value sets that are drawn from the selected code system, whether the code system has been replaced with a more updated version, and the implementation guides that reference the code system.
Proprietary Content
Code systems containing proprietary content are displayed in the Cartos Terminology Browser with relevant metadata and relationships. Cartos does not host or redistribute proprietary code system content; users are directed to the authoritative publisher or steward for access.
Value Sets
To search for a value set, select the Value Sets option from the search drop down menu, enter the name, or a portion of the name, of the value set you are looking for in the search (for example, “US Core” or “US Core Condition Codes”). If you prefer to browse all the value sets in Cartos, click the search icon to perform a blank search and the entire list of value sets will display.
Double click on the value set name to see information about the value set members, version, steward and identifiers. You will also be able to see the code system(s) used in the value set definition, the implementation guides that reference the value set, whether the value set has been replaced with a more updated version, and the value set expansion. The value set expansion display is limited to 250 concepts per code system.
Proprietary Content
Value sets containing proprietary content are displayed in the Cartos Terminology Browser with relevant metadata and relationships however, value set expansions will not display. Cartos does not host or redistribute proprietary code system content; users are directed to the authoritative publisher or steward for access.
Collections
Terminology collections are organized lists of the value sets and code systems required by ONC regulation, organized by implementation guide. Collections help you find the terminology content tied to a specific regulation criterion or implementation guide without searching for each value set or code system one at a time. Users can search collections by regulation criterion, or implementation guide name.
Some IGs were developed some time ago, and terminology assets have evolved since publication. The Cartos team consulted with IG authors to identify the recommended terminology to use. In some cases, this involves acquiring terminology assets from the National Library of Medicine Value Set Authority Center or HL7 terminology.hl7.org (THO) rather than PHIN VADS (as referenced in the IG), and in other cases it involves providing a recommended replacement.
For this scenario, Cartos collections include expansions for value sets referenced in the IG, and for the value sets identified as appropriate replacements.
Proprietary Content
Terminology collections may reference proprietary code systems or value sets. When proprietary content is referenced, a placeholder record is provided with available metadata and guidance about where users can obtain the proprietary terminology content. Cartos does not host, redistribute, or display proprietary concept codes. Users must obtain access to proprietary terminology content directly from the authoritative publisher.
How to View All Collections
If you prefer to browse all the collections in Cartos, select the Collections option from the search drop down menu, then click the search icon. The entire list of collections will display in your search results.
Collections are available for each implementation guide referenced in regulation or SVAP.
To view additional details, double-click the collection name for any row in the search results. Collection details include the creation date, regulation or SVAP references, and code systems and value sets used in the collection.
How to Search by Implementation Guide
Select the Collections option from the search drop down menu, enter a portion of the implementation guide title (“case reporting” or “laboratory” or “C-CDA”), then click the search icon. All collections associated with the search string you entered in the name display in your search results.
Terminology Collections
How Collections are Organized
Terminology content is organized in Cartos by the implementation guide that requires it. Instead of figuring out which code systems and value sets an implementation reference, you can go directly to the collection for the IG-related content you need.
ONC regulation references multiple implementation guides, each with its own terminology requirements. Cartos includes a separate content collection for each IG referenced in ONC rules, enabling you to download only the content relevant to the specific use case you are implementing, without sorting through content you do not need.
Each terminology collection contains:
- Value set expansions for the value sets specified by the IG
- References to code system resources
- Metadata identifying the regulation, IG, and package date
Content scope
Terminology collections generally include all relevant value set expansions with the following exceptions:
- Intensionally defined value sets which contain the entirety of the following code systems (LOINC, RxNorm, SNOMED CT US Edition, ICD-10-CM, ICD-10-PCS and HCPCS), only provide the value set definitions (i.e., ValueSet.compose).
- Value sets with expansions drawn from proprietary code systems are included as a placeholder; however, proprietary concept codes are not available
More information related to content inclusion within Cartos can be found in the section What Content is Available in Cartos.
Collection Creation Cadence and Versioning
Terminology collection updates are released every six months, in alignment with scheduled SNOMED CT US Edition releases. Additional updates may occur for a critical correction or ONC-directed release.
Cartos retains the current collection version and one prior collection version for user reference.
To be notified when new or updated packages become available, sign up for ONC’s weekly email updates and follow us on X and LinkedIn.
Collection Update Release Schedule
Cartos terminology collection updates are planned for release every six months, in June and December. The collection update table and release schedule chart summarize the expected update cycle, target release months, and related terminology content refresh activities.
Collection Index
Cartos includes access to value set expansion collections consisting of ValueSet resources organized by IG.
Find the IG you need in the list below and click on it to download a compressed file containing the value set expansions.
Regulatory Standards
HL7 CDA R2 IG, Quality Reporting Document Architecture Category III (QRDA III), DSTU R1
HL7 CDA R2 IG: Healthcare Associated Infection (HAI) Reports, Release 1 – US Realm
HL7 v2.5.1 IG: Electronic Laboratory Reporting to Public Health, Release 1
HL7 v2.5.1 IG: Immunization Messaging Release 1.5 and Addendum July 2015
HL7 CDA R2 IG: National Health Care Surveys (NHCS), Release 1 – US Realm
HL7 IG: Data Segmentation for Privacy (DS4P), Release 1
HL7® FHIR® IG: Electronic Case Reporting (eCR)—US Realm 2.1.0—STU 2 US (HL7 FHIR eCR IG)
HL7 FHIR Da Vinci Payer Data Exchange (PDex) Implementation Guide, Version 2.1.0 – STU 2.1
HL7 FHIR Da Vinci Prior Authorization Support (PAS) FHIR Implementation Guide, Version 2.0.1 – STU 2
HL7 FHIR Da Vinci—Coverage Requirements Discovery (CRD) Implementation Guide, Version 2.0.1 – STU 2
SVAP
HL7 CDA R2 IG: Consolidated-CDA Templates for Clinical Notes Edition 4.0 – STU 4 (US Realm)
HL7 v2.5.1 IG for Immunization Messaging, R 1.5 2018 Update
HL7 CDA R2 IG: Healthcare Associated Infection (HAI) Reports, R3 – US Realm, Dec 2020
HL7 CDA R2 IG: National Health Care Surveys (NHCS), R1 STU R3.1 – US Realm
2025 CMS QRDA I Implementation Guide for Hospital Quality Reporting, v1.1
2025 CMS QRDA III Implementation Guide for Eligible Clinicians, v1.1
HL7 v2.5.1 IG: Syndromic Surveillance R1 – US Realm STU, July 2019
Terminology Collections and Regulation Context
ONC regulation references specific IG versions that health IT developers participating in the ONC Certification Program must support with a related effective date. Terminology assets and implementation guides change at a pace that is different than regulation.
Sub-regulatory updates via SVAP adopt newer versions of IGs referenced in regulation. Regulatory updates may retire IG versions and adopt a newer version, remove an IG from regulation entirely or add an IG (see HTI-4 below).
Cartos content has been designed to ensure terminology content availability for any IG that is referenced in ONC regulation or SVAP.
HTI-1: Health Data, Technology, and Interoperability: Certification Program Updates, Algorithm Transparency, and Information Sharing
HTI-1 is an ONC final rule that updates the Health IT Certification Program. It expands requirements for interoperability, algorithm transparency, and information sharing, and it references several implementation guides with distinct terminology specifications.
Cartos provides a content collection for each IG where terminology is specified under HTI-1. Users can browse all HTI-1 collections, organized by implementation guide, in the Cartos Terminology Browser.
HTI-4: Health Data, Technology, and Interoperability: Electronic Prescribing, Real-Time Prescription Benefit and Electronic Prior Authorization
HTI-4 requires health IT systems to meet new certification standards for sending prescriptions electronically, checking a patient’s drug costs and coverage in real time, and handling prior authorization requests digitally. Like HTI-1, this rule also references multiple implementation guides with distinct terminology requirements.
Cartos provides a collection for each IG where terminology is specified under HTI-4. Users can browse all HTI-4 collections, organized by implementation guide, in the Cartos Terminology Browser.
Standards Version Advancement Process (SVAP)
The ONC Standards Version Advancement Process (SVAP) lets certified health IT developers voluntarily adopt newer versions of certain standards and implementation guides between rulemaking cycles. This allows organizations to stay current with evolving standards without waiting for a new final rule.
Cartos supports SVAP by providing the content associated with SVAP-approved standards versions. If you are implementing an SVAP-approved version of an IG, check the relevant collection in Cartos Terminology Browser to confirm which content versions are available.
What Content is Available in Cartos?
Cartos – ONC’s terminology service provides value sets and code systems referenced in ONC regulation and interoperability standards. Use the Cartos Terminology Browser to view the available content, canonical URLs, object identifiers (OIDs), and versions. This section explains what Cartos includes and how versions are managed.
Code Systems
Cartos includes the code systems used for value sets required by ONC regulation and interoperability standards. Certain code systems have established distribution mechanisms or licensing restrictions. In those cases, Cartos provides metadata, references, and related value set information while directing users to the steward for full code system access.
Proprietary Code Systems
Proprietary code systems that require separate licensure are out of scope for Cartos and are not available as CodeSystem resources. Links to access this content directly are provided in the table below. If your implementation requires one of these code systems, you must obtain it directly from the steward.
| Code System | Link to Access |
|---|---|
| Current Procedural Terminology (CPT) | AMA CPT Home Page |
| National Uniform Billing Committee Codes (NUBC) | NUBC Home Page |
| Code on Dental Procedures and Nomenclature (CDT) | ADA CDT Home Page |
| American Joint Committee on Cancer (AJCC) | AJCC Home Page |
| X12 Service Type Codes | X12 Service Type Code Page |
| All Patient Refined Diagnosis Related Groups (APR-DRGs) | APR-DRGs Home Page |
| National Council for Prescription Drug Programs (NCPDP) | NCPDP Home Page |
| Standard Terminology for Medical Products of Human Origin (ISBT 128) | ISBT 128 Licensing Page |
ValueSet and CodeSystem resources with metadata are provided as placeholders in Cartos; however, value set expansions containing proprietary concept codes are not available. Cartos includes a clear message in the ValueSet metadata explaining why the expansion content is not available. Users should obtain proprietary code content directly from the steward.
Code Systems with Established Distribution
Several code systems referenced in the ONC Certification Program have established distribution systems and are not available as CodeSystem resources on Cartos. The following table includes links to access and browse the entirety of the code systems listed below. Expansions for value sets drawn from these code systems are available, subject to limitations described within Rate Limits and Fair Use section.
| Code System | Link to Access |
|---|---|
| SNOMED CT (US Edition) | SNOMED CT |
| LOINC | LOINC |
| RxNorm | RxNorm |
| ICD-10-CM ICD-10-PCS | ICD-10-CM and ICD-10-PCS |
| HCPCS | Healthcare Common Procedure Coding System (HCPCS) |
| ICD-9 | ICD-9-CM |
| NDC | NDC |
Code System Versions
Cartos terminology operations generally return code system and value set expansion content with the most recently published code system version. Exceptions include specific code system versions referenced in implementation guides. When an implementation guide specifies a specific version, Cartos provides that version so you can access exactly what your IG requires.
Value Sets
Cartos includes a comprehensive, vetted repository of all value sets referenced in implementation guides associated with the following nationally recognized standards, not only those value sets required for ONC Health IT certification testing.
This means that Cartos encompasses the full set of value sets defined within each standard’s implementation guide(s), including those that support optional, contextual, or extended use cases beyond the minimum set exercised during certification testing.
Note that ValueSet resources containing concepts from proprietary code systems will be provided as a placeholder for reference. Proprietary content will not be reflected in the value set expansions.
In certain cases, users may need to expand a value set that contains the entirety of a code system or may result in a large expansion drawn from a subset of code system concepts. The maximum number of concepts returned in a single ValueSet $expand operation is 2,000 per page.
Licensing Summary for Code System Content
The table below summarizes common licensing terms. Review each content steward’s terms for complete requirements.
| Code System | Overview | Link to Learn More |
|---|---|---|
| SNOMED CT (US Edition) | Requires an affiliate license. US users can license for free through the National Library of Medicine’s (NLM) US affiliate agreement, subject to attribution and use restrictions. | SNOMED International |
| LOINC | Publicly available; with attribution; copyright held by and maintained by Regenstrief Institute. | LOINC |
| RxNorm | Publicly available; from NLM. | RxNorm |
| ICD-10-CM | Publicly available; no license required, the Centers for Disease Control (CDC) | ICD-10-CM |
| ICD-10-PCS | Publicly available; no license required, the Centers for Disease Control (CDC) | ICD-10-PCS |
| CVX / MVX | Publicly available; maintained by the Centers for Disease Control (CDC) | CDC |
| NDC | Publicly available; maintained by the Federal Drug Administration (FDA) | FDA |
Cartos Terms of Use
Using Cartos (including the API, web browser, and collection downloads) means you agree to ONC’s Terms of Use.
- Using Cartos, including Cartos Terminology Browser, Cartos API, and terminology collection downloads, means you agree to use the service responsibly and follow all applicable terminology licensing and use requirements.
- The Cartos API is intended for health IT integration, implementation, validation, testing, and research. Do not use Cartos to bulk-harvest content beyond what your implementation reasonably requires.
- Users are responsible for following the licensing, attribution, redistribution, and use requirements for each code system or terminology steward represented in Cartos. If you download or redistribute content, you must follow the applicable licensing terms for each terminology resource included in that content.
- Some terminology content may be limited, unavailable, or provided only as metadata because of licensing restrictions, steward distribution requirements, or technical constraints.
- Misuse of Cartos, including attempts to bypass rate limits, overload the service, scrape excessive content, or use automated workarounds, may result in rate limiting, blocking, or suspension of access.
- Cartos does not replace official content stewards, source terminology licensing requirements, implementation guides, regulations, or organizational compliance review.
Support Resources
End users may submit support requests through the ONC Cartos Support Portal.
When submitting a support request, users should include enough detail for the Cartos team to review, assess, and route the request appropriately. Providing complete information will help support timely triage, technical review, terminology review, and follow-up.
Helpful information may include:
- Value set or code system name
- Canonical URL or identifier
- Version
- API request or endpoint used
- Error message or response code
- Related regulation, SVAP, or implementation guide
- Description of the issue or requested change
- Requested rate-limit change, if applicable
ONC will review submitted requests and coordinate technical routing or terminology review as needed.