SNOMED CT 101: A guide to the international terminology system

Need a brief refresher on the basics of what SNOMED CT® codes are and how they work? Brush up on this coding system with our SNOMED CT 101 guide.
SNOMED CT 101 Guide

When it comes to understanding the various standardized code sets linked to clinical terminology, it’s easy to get overwhelmed. But don’t fret; this handy guide answers foundational questions about SNOMED CT and provides some additional resources that will have you up to speed in no time.

Table of Contents

What is SNOMED CT?

SNOMED CT stands for Systemized Nomenclature of Medicine – Clinical Terms. It is a standardized, international, multilingual core set of clinical healthcare terminology that can be used in electronic health records (EHRs). SNOMED International is the non-profit standards development organization that creates and distributes SNOMED CT, and it is operated by the International Health Standards Development Organization.

Why is SNOMED CT used?

SNOMED CT represents coded terms that may be used within EHRs to capture, record, and share clinical data for use in healthcare organizations. It is a key component supporting solutions that enable the retrieval of meaningful clinical information. SNOMED CT terms, or codes, have been used internationally for years, and they became widely used in the United States after 2013 when the federal government required EHRs to include the terminology in their systems in order be compliant with Stage 2 of Meaningful Use.

How is SNOMED CT maintained?

SNOMED International continuously updates content mainly based on user needs and feedback. Updates to SNOMED CT International are released annually on January 31 and July 31. The United States edition of SNOMED is updated by the National Library of Medicine twice a year, in March and September.

What do the codes look like?

SNOMED CT codes are numerical and are a minimum of six digits long. For instance, 271737000 is the unique code for the SNOMED concept anemia (disorder).

How is the terminology organized?

There are four primary categories of SNOMED CT: concepts, descriptions, relationships, and reference sets:

SNOMED CT hierarchy


Concepts, or terms, are represented by unique codes and human readable descriptions. Each concept is a unique clinically relevant thought, across a wide range like abscess, zygote, measurement procedure, or substance, as examples. Currently, SNOMED CT contains approximately 352,567 concepts and is organized by relationships into hierarchies that range from general to detailed.


Descriptions are human readable terms linked to concepts. Concepts can have multiple descriptions, each of which is a synonym of the original concept.


In order to provide meaning to SNOMED concepts, SNOMED uses relationships between concepts to provide formal definitions and organization. For instance, the SNOMED concept viral pneumonia has a defining relationship between is a type and infective pneumonia.


Reference sets are used to customize a version of SNOMED CT or to provide a collection of SNOMED concepts. Examples of reference sets are: The designation of language preferences for specific terms, mapping to other code systems, and a collection of concepts relevant to a medical specialty.

Up to speed on SNOMED CT? Find more 101-style guides, here.

References: Vendor Introduction to SNOMED CT and SNOMED CT Compositional Grammar Specification and Guide
SNOMED and SNOMED CT® are registered trademarks of SNOMED International
.CPT is a registered trademark of the American Medical Association. All rights reserved.

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