# SNOMED CT to UCUM map for units of measure (\<767524001)

**URL:** <https://forums.snomed.org/t/snomed-ct-to-ucum-map-for-units-of-measure-767524001/1541>\
**Category:** Drugs Extension User Group\
**Created:** [August 19, 2026, 5:12am UTC](https://forums.snomed.org/t/snomed-ct-to-ucum-map-for-units-of-measure-767524001/1541 "2026-08-19T05:12:48Z")\
**Posts on this page:** 1\
**Showing post:** 7

<div class="post-metadata">

**Author:** ![mcordell](https://dub1.discourse-cdn.com/flex014/user_avatar/forums.snomed.org/mcordell/32/325_2.png) [@mcordell](https://forums.snomed.org/u/mcordell)\
**Post date:** [November 5, 2026, 4:01am UTC](https://forums.snomed.org/t/snomed-ct-to-ucum-map-for-units-of-measure-767524001/1541/7 "2026-11-05T04:01:15Z")

</div>

As a follow up, I presented this topic to the CMAG at the [October meeting (slides in agenda)](https://conf.spaces.snomed.org/wiki/spaces/cmag/pages/1226833921/2026-10-21+-+CMAG+Meeting).

I’ve since built a demonstrator to help illustrate the use case for such a concept map:  
[UCUMverter - UCUM unit conversion demo](https://mattcordell.github.io/callistemon/ucumverter/).

How it works:

- The **Drug selection** panel (3) is the only place SNOMED CT is used. You pick an AMT drug concept, and its strength (value and SNOMED CT unit) is read from Ontoserver.
- Every unit field in the app is UCUM coded. The lab and creatinine fields use LOINC codes to choose which UCUM units are offered.
- A draft map converts the drug’s SNOMED CT unit to UCUM. This is the only SNOMED CT to UCUM step.
- All unit conversion after that is done in UCUM, using the official NLM [lhncbc/ucum-lhc](https://github.com/lhncbc/ucum-lhc) library.

This is the complete (informal) map the demonstrator uses:

```json
{
  "_comment": "DRAFT 1:1 map from SNOMED CT-AU unit concepts (as used in AMT strength properties) to UCUM codes.",
  "map": {
    "258684004": { "display": "mg", "ucum": "mg" },
    "258682000": { "display": "g", "ucum": "g" },
    "258685003": { "display": "microgram", "ucum": "ug" },
    "258773002": { "display": "mL", "ucum": "mL" },
    "258770004": { "display": "L", "ucum": "L" },
    "258774008": { "display": "microlitre", "ucum": "uL" },
    "258718000": { "display": "mmol", "ucum": "mmol" },
    "258719008": { "display": "micromol", "ucum": "umol" },
    "258798001": { "display": "mg/mL", "ucum": "mg/mL" },
    "258796002": { "display": "mg/L", "ucum": "mg/L" },
    "258797006": { "display": "mg/dL", "ucum": "mg/dL" },
    "258801007": { "display": "microgram/mL", "ucum": "ug/mL" },
    "258799009": { "display": "microgram/L", "ucum": "ug/L" },
    "258806002": { "display": "nanogram/mL", "ucum": "ng/mL" },
    "258802000": { "display": "microgram/g", "ucum": "ug/g" },
    "258803005": { "display": "microgram/kg", "ucum": "ug/kg" },
    "258997004": { "display": "international unit", "ucum": "[iU]" },
    "732935002": { "display": "each", "ucum": "{each}" }
  }
}

```

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_[View the full topic](https://forums.snomed.org/t/snomed-ct-to-ucum-map-for-units-of-measure-767524001/1541)._