LOINC code lookup and validator.

What a LOINC code is

LOINC (Logical Observation Identifiers Names and Codes) is the standard code system for laboratory tests and clinical observations. A code looks like 2345-7: a number of up to seven digits, a hyphen and one check digit. Labs, electronic health records and health-data exchanges use it so that "glucose in serum" means the same thing everywhere.

The six parts of a LOINC name

• Component: what is measured, such as Glucose or Hemoglobin A1c.
• Property: the kind of quantity, for example MCnc (mass concentration) or SCnc (substance concentration). This is where mg/dL versus mmol/L shows up.
• Time: usually a point in time; 24H means a 24-hour collection.
• System: the specimen, such as Ser/Plas (serum or plasma), Bld (blood) or Urine.
• Scale: Qn quantitative, Ord ordinal, Nom nominal.
• Method: optional, such as a particular assay.

The check digit

The final digit is a modulus-10 check digit calculated from the digits before the hyphen: from the right, double every other digit (subtracting 9 when a doubled digit exceeds 9), add everything, and the check digit is the amount needed to reach the next multiple of 10. For 2345-7: from the right, double the 5 and the 3 (10 becomes 1 after subtracting 9, and 3 becomes 6), keep the 4 and the 2, add 1+4+6+2 = 13, and the check digit is 10 − 3 = 7. The tool does this for you and shows the expected digit when yours fails. A valid check digit only shows the code is well-formed; it does not prove the code exists.

Sources

Search data: NLM Clinical Table Search Service, LOINC items. LOINC is copyright Regenstrief Institute and available under the LOINC licence. The check-digit rule is documented in the LOINC User's Guide. TNAADO does not store searches.

Frequently asked questions

How do I find the LOINC code for a lab test?

Type the test name and specimen, for example glucose serum, and read the component, property and system of each result to pick the one that matches your report.

How is a LOINC check digit calculated?

It is a modulus-10 digit computed from the numbers before the hyphen. This page calculates it and shows the expected digit if yours is wrong.

Why are there many codes for glucose?

LOINC separates tests by specimen, timing, method and unit type, so each variant has its own code. Choose the one whose system and property match your test.

Does LOINC tell me what a result means?

No. It only identifies the test. Reference ranges and interpretation come from the laboratory and your clinician.