> For the complete documentation index, see [llms.txt](https://docs.snomed.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.snomed.org/implementation-guides/loinc-implementation-guide/about-loinc/2.-what-is-loinc.md).

# What is LOINC?

### Purpose and Scope <a href="#id-2.whatisloinc-purposeandscope" id="id-2.whatisloinc-purposeandscope"></a>

LOINC (Logical Observation Identifiers Names and Codes) is the international terminology standard for identifying health observations, measurements, and document types in healthcare information systems, such as electronic health records (EHRs)

LOINC provides a set of universal codes and names for laboratory and clinical observations, including measurements like blood pressure and cholesterol levels, and clinical assessments like standardized questionnaires and surveys that collect comprehensive information from patients to diagnose their health and are used to determine their appropriate treatment plan. These codes allow for interoperability between different healthcare systems, enabling seamless exchange and aggregation of health data.

### LOINC Basics <a href="#id-2.whatisloinc-loincbasics" id="id-2.whatisloinc-loincbasics"></a>

* A LOINC concept is represented by a code and a corresponding name, e.g. [8480-6](https://loinc.org/8480-6) Systolic blood pressure.
* LOINC codes are unique and permanent, though codes can be deprecated or discouraged and replaced by an alternate concept.
* There are over 100,000 concepts represented in LOINC, each distinguishing the given observable.
* There are two releases of LOINC each year in February and August. It is strongly recommended that the most current version of LOINC is used, and that it is implemented within 90 days of release.
* LOINC use is bound by the LOINC License. In general, LOINC codes are licensed free-for-use for all purposes except the creation of a competing code system.

### LOINC Resources <a href="#id-2.whatisloinc-loincresources" id="id-2.whatisloinc-loincresources"></a>

* [LOINC Primer](https://loinc.org/get-started/)
* [LOINC User Guide](https://loinc.org/kb/users-guide/)
* [LOINC Knowledge Base](https://loinc.org/kb/)
* [SearchLOINC](https://loinc.org/search/)
* [LOINC Hierarchy Browser](https://loinc.org/tree/)
* [LOINC Terminology Service using HL7 FHIR](https://loinc.org/fhir/)
* [LOINC Community Forum](https://forum.loinc.org/)

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