ValueQuantity

ValueQuantity is a data construct used to represent a measured amount as a numeric value paired with a unit. It appears in data models, APIs, and health and scientific data formats as a portable way to express quantities such as length, mass, volume, or dose, where both the magnitude and the unit are important for interpretation and calculations.

Typically, a valueQuantity contains fields such as value (the numeric amount), unit (a human-readable unit name), system (a URI identifying the unit system, for example UCUM or SI), code (the unit code within that system), and sometimes an optional comparator (for indicating whether the value is less than, greater than, or approximately equal to a threshold). Some data schemas implement valueQuantity as a wrapper for a Quantity or as a choice-type element where a field can hold a quantity or other value types.

In practice, valueQuantity is commonly used in health care data interchange, laboratory results, medication dosages, and other measurement data. Standards like HL7 FHIR define a Quantity data type with similar fields, and many implementations expose a valueQuantity wrapper in JSON or XML to facilitate consistent handling of numeric quantities across systems. When designing or consuming such data, attention to unit systems, code mappings, and unit normalization is important to enable reliable comparisons and calculations.

See also: units of measure, UCUM, quantity data type, data interoperability, health information exchange.