This document describes requirements for collections of metadata about data elements and their containing models and datasets in a healthcare environment. The collection can serve as a repository or as dictionary describing a set of items in use in a particular domain, organisation or product for reference, or it can additionally serve as a registry, supporting the development and communication of standard items to an audience with shared goals. This document specifies standard refinements that account for the detailed governance and administration requirements that are particular to healthcare data. It focuses on the description of data that is persisted in healthcare systems rather than the specification of messages between these systems. It describes necessary extensions to the ISO/IEC 11179 series and to other International Standards on metadata originating from ISO/IEC JTC 1/SC 32 to address the wider variety of value domain types found in healthcare. Where appropriate, it also suggest restrictions/simplifications to the ISO/IEC 11179 series that promote wider adoption without compromising interoperability between metadata registries and opportunities for the development of tooling that consumes metadata for the generation or the parameterization of code.