Short answer: LOINC (Logical Observation Identifiers Names and Codes) is a free, international code system that gives each laboratory test and clinical measurement its own identifier. HbA1c is 4548-4, serum creatinine is 2160-0, heart rate is 8867-4. When two labs use the same LOINC code, a system can put their results on the same chart, even if the labs print different names on paper.
Who maintains it and how it is built
LOINC is maintained by the Regenstrief Institute in the United States and is free to use. Codes are a number, a hyphen and a check digit (for example 2345-7). Each code has a fully specified name made of six parts:
- Component: what is measured (glucose).
- Property: the kind of quantity (mass concentration).
- Time: a point in time or a period (for example 24 hours).
- System: the specimen (serum or plasma, urine, blood).
- Scale: quantitative, ordinal, nominal.
- Method: when the method changes the meaning (LDL calculated 13457-7 vs LDL direct 18262-6).
That is why there can be several codes for what looks like one test: glucose in serum (2345-7), fasting glucose (1558-6) and glucose in whole blood (2339-0) are different measurements.
Where you meet LOINC
As a patient, you rarely see the code on paper, but it is behind the result in electronic records, lab portals and health apps. In HL7 FHIR, the code of an Observation is usually a LOINC code; national programmes in Europe and the US require it for lab results. For developers, mapping a lab's local codes to LOINC is often the hardest part of an integration.
In Anpheros
In Anpheros every lab value is stored with its LOINC code, read from the report or mapped from the lab's own name, so results from different labs line up on one chart. Our pages on individual tests, such as the HbA1c test and the lipid panel, list the codes you will find. Developers: see FHIR code systems and the lab results API.
Related pages
- UCUM units in lab results
- What is SNOMED CT? Clinical terms as codes, explained simply
- FHIR Observation explained
- LOINC vs SNOMED CT
- How to map local lab codes to LOINC, step by step
- FHIR terminology servers explained
Sources
Frequently asked questions
Is LOINC free?
Yes. LOINC is free to use; you accept its licence terms when you download it from the Regenstrief Institute.
What is the difference between LOINC and SNOMED CT?
LOINC names the test or measurement (what was asked); SNOMED CT describes clinical findings, diagnoses and procedures, and is often used for results that are not numbers. They are used together.
Why does the same test have several LOINC codes?
Because the specimen, the time period or the method change the meaning, for example LDL calculated (13457-7) and LDL direct (18262-6).
Do patients need to know LOINC codes?
No. But a health app that stores them can merge and compare results from different labs correctly.
Try it free in the sandbox
Your first FHIR call in 5 minutes. An HL7 FHIR R4 API with the patient's consent built in: try it in the sandbox, then connect your own app or clinic system.
Free · 30 synthetic patients · no card
Anpheros builds a medical record that the patient controls and can share with any clinic, on an HL7 FHIR R4 platform, based in the EU. These guides help you understand and organise your health; they do not replace your doctor.
About Anpheros →
AnpherosThe more you log, the clearer your record
Your health history in one place, under your control.
Free · Works in your browser · No card
