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LOINC Overview

by Daniel Vreeman last modified 2010-12-21 12:55
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LOINC Overview Questions

FAQ overview

What is LOINC?

LOINC (Logical Observation Identifiers Names and Codes) was developed to provide a definitive standard for identifying clinical information in electronic reports. The LOINC database provides a set of universal names and ID codes for identifying laboratory and clinical test results in the context of existing HL7, ASTM E1238, and CEN TC251 observation report messages. One of the main goals of LOINC is to facilitate the exchange and pooling of results for clinical care, outcomes management, and research. LOINC codes are intended to identify the test result or clinical observation. Other fields in the message can transmit the identity of the source laboratory and special details about the sample.

What is RELMA?

RELMA (Regenstrief LOINC Mapping Assistant program) helps users map their local terms or lab tests to universal LOINC codes. RELMA contains many tools that will help you search for the correct LOINC codes to map to your tests.

How are LOINC and RELMA distributed? How often are updates to LOINC and RELMA released?

LOINC is available as an Microsoft Access (.mdb) database file and also a comma delimited text file (.csv). 

RELMA is available as a desktop mapping program for the Microsoft Windows platform. (Sorry Mac, Linux and other OS users. You can use the program to search the latest version of LOINC right from your browser or setup a virtual machine to run Windows). 

The RELMA package includes the LOINC table.  

You can download LOINC, RELMA, and other accessory files right from this website:

New versions of RELMA and LOINC are released twice a year, in June and December. 

Are there any training or workshops on the use of LOINC codes and RELMA?

Yes, there are workshops in June and December.  You may register for the next set of workshops at Meetings.  Until you are able to attend a workshop, on-line training materials can be found at Slideshows.

In what languages are LOINC, RELMA, and the associated users' guides available?

LOINC has been translated into many different languages, and new translations continue to sprout up. Visit the International section of this website for more information. Regenstrief accommodates more than one version (we call them "linguistic variants") of any given language. We recently published a paper describing our approach to translations.


Who is using / mapped to LOINC?

LOINC and RELMA are widely used, in part because they have always been freely available. We do not have a definitive list of adopters, but we have created an online adopter directory and welcome information regarding new users and their use cases.

If your organization has adopted LOINC, you can have your profile listed here on the LOINC website by completing the profile form here.
(Requires a login to this site. If you don't have a login, create one here)


Also, be sure to take a look at to see a map of countries with LOINC users.

Are there any professional organizations that certify personnel to perform LOINC mapping?

At this time, Regenstrief does not provide or authorize a LOINC mapping certification for organizations or individuals. We have created a voluntary online directory of LOINC adopters at as a reference. Some of the organizations in this directory do offer LOINC mapping as a service.

How do I obtain a license for my organization to adopt LOINC codes?

Regenstrief Institute distributes LOINC and RELMA free of charge.  In obtaining and using LOINC or RELMA, you agree to the terms-of-use that are outlined at  No extra approval process from Regenstrief Institute is necessary for use consistent with these terms. 

Are there any articles or publications regarding LOINC?

Numerous articles and publications can be found at Documentation

Case Sensitivity

All LOINC names are case insensitive. Senders and receivers may use upper, lower, or mixed case. Meanings should NOT be sensitive to case conversion to avoid the possibility of confusion when the information is sent over networks that may apply case conversion. For the few names that ARE case sensitive by international convention, such as red blood cell antigens, we use the word 'LITTLE' in front of the the letter that is lower case. Superscripts are indicated by the word "SUPER'.

What kind of hierarchy does LOINC have?

Computable hierarchies exist in LOINC, but are not currently exposed in a relational or semantic network format that would be easy for a terminology server to consume. The hierarchy can be graphically displayed by clicking on "Set Hierarchy and Search Limits" tab in RELMA, component hierarchy tab, then clicking on "+" sign next to items you are interested in.

Where can I find previous versions of LOINC to download?

For the majority of users, the most recent LOINC version is the one you want. It is always our best one yet. 

LOINC follows good terminology development principles, which means that LOINC codes are never removed from the database and meaning of a code is never changed over time. So, all of the LOINCs that have ever existed are present in the most recent release. Over time and with each release, we add new terms and accessory content and make revisions where needed. For example, if we notice that we inadvertently have two codes with slightly different names but the exactly the same meaning, we’ll deprecate (retire) one of the codes and add a pointer to the preferred term. So, in the vast majority of cases, if you want LOINC, you want the most recent version.

We do make our archive of past LOINC releases available as part of our Premium Membership program. Past releases are available for direct download from the membership site or via an FTPS server.

If you are wondering about all of this because of the Meaningful Use specifications in the United States, please read this FAQ entry too.

The Meaningful Use regulations specify a particular version of LOINC. Do I have to use that version, or can I use the latest version?

The Meaningful Use Stage 2 Final Rule states in a couple of places that they have created a mechanism for using newer versions of LOINC than the versions available at the time the rule was promulgated. Basically, yes you can use the newer version, unless the HHS Secretary specifically prohibits it (which we think would be unlikely). Here are a couple of excerpts that discuss this change:

[Federal Register /Vol. 77, No. 171 /Tuesday, September 4, 2012 /Rules and Regulations 54247]

We have established a process for adopting certain vocabulary standards, including SNOMED CT® and LOINC®, which permits the use of newer versions of those standards than the one adopted in regulation. We refer readers to section IV.B for a discussion of ‘‘minimum standards’’ code sets and our new more flexible approach for their use in certification and upgrading certified Complete EHRs and certified EHR Modules. Readers should also review § 170.555, which specifies the certification processes for ‘‘minimum standards’’ code sets.

[Federal Register /Vol. 77, No. 171 /Tuesday, September 4, 2012 /Rules and Regulations 54269]

We appreciate the comments submitted in support of our proposal and are revising § 170.555 such that, unless the Secretary prohibits the use of a newer version of a ‘‘minimum standards’’ code set identified in subpart B of part 170, the newer version could be used voluntarily for certification and implemented as an upgrade to a previously certified Complete EHR or certified EHR Module without adversely affecting the EHR technology’s certified status.


Here is the extract from 170.555 [Federal Register / Vol. 77, No. 171 / Tuesday, September 4, 2012 / Rules and Regulations 54292]:

§ 170.555 Certification to newer versions of certain standards.

(a) ONC–ACBs may certify Complete EHRs and/or EHR Module(s) to a newer version of certain identified minimum standards specified at subpart B of this part, unless the Secretary prohibits the use of a newer version for certification.

(b) Applicability of a newer version of a minimum standard. 

(1) ONC–ACBs are not required to certify Complete EHRs and/or EHR Module(s) according to newer versions of standards identified as minimum standards in subpart B of this part, unless and until the incorporation by reference of a standard is updated in the Federal Register with a newer version.  

(2) A certified Complete EHR or certified EHR Module may be upgraded to comply with newer versions of standards identified as minimum standards in subpart B of this part without adversely affecting its certification status, unless the Secretary prohibits the use of a newer version for certification.

How do I process the CSV format of the LOINC table that replaced the tab-delimited one?

Starting with LOINC version 2.46 (December 2013), a comma-separated values (CSV) file is the only text format distribution of the LOINC table (i.e., we no longer provide the tab-delimited format). 

We decided to switch formats to provide our files in more standardized and universally accepted format. One of the reasons we selected the .csv format was because of the  “Internet Engineering Task Force” (IETF) the “Common Format and MIME Type for Comma-Separated Values (CSV) File” standard, RFC 4180. By using a file format based on an internationally recognized published standard we can be sure that our users will be able to understand the file layout and structure. If you are interested, the standard is freely available at The loinc.csv file that we deliver fully complies with rfc4180 standard. 

Most spreadsheet applications (Excel, OpenOffice Calc, etc) recognize and should be able to open the CSV format. We have provided basic scripts and related files to help import the table into Oracle and MySQL; these supplementary files are included in the zip file with the LOINC table in CSV format. 

A couple of points worth noting about dealing with the CSV format file:

Use of double quotes 

Section 2.6 of the standard states: “6.  Fields containing line breaks (CRLF), double quotes, and commas should be enclosed in double-quotes. “

If you are writing your own parser for the file, your code should look for and expect the field contents to be surrounded by double quotes as specified in sections 2.5 and 2.6 of the standard.

If you need a TAB delimited file, you still have a couple of options

We continue to distribute the LOINC database in Microsoft Access format. It would be very simple to export the table from Access into a TAB delimited file. You could also open the loinc.csv file in Microsoft Excel and then use the “Save As” option to store it as a TAB delimited file. Finally, a Google search for “csv to tab delimited” returns many options for converting .csv files to TAB delimited and other file formats. 

Some notes about Excel

Microsoft Excel 2003 (included with Office 2003) has a maximum row limit of 65,536. This is problematic for looking at the LOINC table, because we now have over 73,000 terms :-).

Also, Excel likes to be helpful and auto-format some cells. Watch out for formatting in the LOINC_NUM field that can turn things like the LOINC code "1-8" into "8-Jan".

Should the UCUM unit bracket characters be included on a lab report?

In general, UCUM unit brackets should be included because they have specific meaning that will be lost if they are removed. 

UCUM units contain two different types of brackets -- square ([ and ]) and curly ({ and }). Curly brackets are also called curly braces. Square brackets indicate special, non-metric units (such as international unit = [IU]) or those specifically used in the U.S. or Britain (such as dram (US and British) = [dr_av]). They also are used in place of parentheses in HL7's "ISO+" codes that use parentheses as part of the unit symbol, such as "(ka_u)", which is represented by [ka_u] in UCUM (see for more details). 

In UCUM, curly brackets are annotations (ignored by parsers, but helpful to humans). They are used to represent strings that are not formally defined UCUM units of measure, such as {Ratio}, {copies}, or {beats}/min.


Current Versions
LOINC 2.59
Released: 2017-02-21

RELMA 6.18
Released: 2017-02-21

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