In our position paper published in Clinical Chemistry and Laboratory Medicine, we address a problem that has persisted for more than 30 years: laboratory medicine in eastern and western Germany still uses different measurement units. While eastern German states largely adopted SI units (e.g., mmol/L for glucose), western states continue to rely on conventional units (e.g., mg/dL). We illustrate the clinical risk with straightforward examples — a glucose value of “20” could indicate life-threatening hypoglycaemia in one system or severe hyperglycaemia in the other. Since clinicians routinely communicate lab values verbally without mentioning the unit, this inconsistency puts patients at risk.

Beyond direct patient care, we argue that standardized units are necessary for semantic interoperability in digital medicine. Germany’s electronic patient record (ePA) will collect laboratory results from multiple providers, and patients will naturally expect that values from different laboratories are comparable. Without uniform units, that expectation becomes a source of error. Our working group proposes a table of recommended units for a range of clinically important measurands. Where our table does not cover a specific analyte, we provide a set of decision criteria for deriving the appropriate unit: concentrations should always be expressed per litre, with the numerator chosen to yield clinically meaningful numbers. If the molecular weight of the measurand is known, amount-of-substance units (mol-based) are preferred over mass units.

The issue becomes even more pressing in light of the European Health Data Space (EHDS). Under Regulation (EU) 2025/327, cross-border exchange of laboratory results is scheduled to become operational by March 2031. The EHDS requires Member States to ensure that laboratory and diagnostic reports are interoperable across borders in a common European exchange format. If we cannot agree on consistent units within Germany, participating meaningfully in EU-wide data exchange will be difficult.

In an accompanying editorial, Zaninotto and Plebani endorse our proposal and call on international federations and national societies to work toward coordinated implementation of harmonized measurement units. They frame this not only as a technical question but as a matter of transparency, equity, and the patient’s right to receive clear, comparable laboratory data.

https://doi.org/10.1515/cclm-2026-0075 https://doi.org/10.1515/cclm-2026-0343