What Is ICD-11?

The 11th revision of the International Classification of Diseases (ICD-11) is the global standard for recording, reporting, and analyzing health information, providing a universal language of codes and rules that allows health professionals and health systems around the world to share and compare data.

The 72nd World Health Assembly adopted ICD-11 in May 2019, and ICD-11 came into effect for WHO member states on Jan. 1, 2022, although national implementation timelines vary, according to the World Health Organization (WHO). When and how the United States will implement ICD-11 remains to be seen, but now is the time to start learning about what this transition could look like.

Reviewing some distinguishing characteristics of ICD-11 will give you a better idea of what to expect as the transition to ICD-11 approaches, including how to address its impact on current practices, so you can start devising a plan for moving forward.

Why Do We Need ICD-11?

ICD-11, like previous versions of ICD, provides a way to translate diagnoses into alphanumeric codes. This shared language enables standardized reporting, monitoring, and comparison of diseases, injuries, and other health conditions (morbidity), as well as causes of death (mortality), worldwide.

ICD codes can have enormous financial importance, as they also are used to determine resource allocation, such as funding for health initiatives. In countries where ICD codes are the basis for health insurance billing, such as the United States, ICD is closely tied to healthcare finances and provider reimbursement.

WHO, which is responsible for maintaining and publishing ICD, adopted ICD-10 through the World Health Assembly in 1990. As medical knowledge and health information needs evolve, ICD-10 is increasingly limited in its ability to provide the precision and flexibility available in ICD-11. The 2019 version is the latest WHO version of ICD-10. Future enhancements are being introduced in ICD-11, although WHO may still deploy emergency codes in ICD-10 when needed.

Many countries use ICD modifications, such as the United States’ clinical modification, ICD-10-CM. Differences among national modifications can limit direct international comparability of morbidity data and complicate links between classifications, guidelines, and other health information resources.

ICD-11 Structure and Digital Focus

ICD-11 represents the first major revision of ICD in more than 30 years. Following extensive international collaboration and review, the 72nd World Health Assembly adopted ICD-11 in May 2019. This newest edition, over a decade in the making, reflects significant advances in science and medicine and introduces substantial changes in how health conditions are classified, coded, and reported.

ICD-11 underwent a major redesign. At its core is the ICD-11 Foundation, a multidimensional knowledge base containing interconnected health concepts and related information. Statistical classifications for particular uses can be derived from this Foundation. The principal statistical classification derived from the ICD-11 Foundation is ICD-11 for Mortality and Morbidity Statistics (ICD-11 MMS). To bring ICD into the 21st century, updates include a digital design; easy integration with electronic health applications and information systems; improved ability to address multiple topics, such as capturing healthcare quality and patient safety data; and a more user-friendly format. ICD-11 uses linearizations, which are ways of organizing diseases and health conditions into classifications designed for specific purposes, such as reporting mortality and morbidity, supporting primary care and research, and monitoring public health.

These advancements have made ICD-11 more detailed, flexible, and digitally integrated than its predecessors. ICD-11 is designed to work with other classifications and terminologies. For example, it can be used together with the International Classification of Functioning, Disability and Health (ICF), and its rare-disease content is regularly updated in collaboration with Orphanet. WHO is also working toward greater interoperability with terminology systems such as SNOMED CT.

In addition to being able to produce digital documentation on a granular level, ICD-11, for the first time, enables "dual coding of traditional medicine diagnoses alongside mainstream medicine and now also permits the generation of a functioning score based on the WHO Disability Assessment Schedule (WHODAS),” according to the WHO Implementation or Transition Guide. The supplementary chapter is optional and is not intended for mortality reporting; coding should also include a category from the main ICD-11 chapters.

What’s New in ICD-11: Postcoordination

ICD-11 codes look different from those in ICD-10 and use a different structure. One important feature of ICD-11 is postcoordination, which allows multiple codes to be combined to add clinical detail that is not contained in a single code. The resulting combination of codes is called a code cluster.

Postcoordination may involve stem codes and extension codes. A stem code represents a condition or other concept that can be used alone when appropriate. An extension code provides additional information about a stem code, such as laterality, severity, anatomy, or other characteristics. Extension codes cannot be used alone for primary classification coding or as the first code in a code cluster.

Cluster coding is combining two or more ICD-11 codes to describe a documented clinical concept. This approach is how ICD-11 explicitly marks codes that are postcoordinated to describe one condition. When a diagnostic statement is broken down into its component parts for simplicity, there needs to be a way to link them in the coded record; clustering is the feature that enables linking. It allows stem codes to be linked when required or permitted and allows extension codes to add applicable detail to stem codes. Cluster coding uses a forward slash (/) to separate stem codes and an ampersand (&) to associate extension codes with the stem code they modify.

This example will help you visualize the concept of postcoordination in ICD-11. Code details are from the January 2026 version of WHO’s ICD-11 Coding Tool.

ICD-11 coding example:

Diagnosis: Left hip osteoarthritis with chronic pain from persistent inflammation

FA00.Z Osteoarthritis of hip, unspecified

Postcoordination:

- Laterality (use additional code, if desired): XK8G Left

- Has manifestation (use additional code, if desired): MG30.30 Chronic secondary musculoskeletal pain from persistent inflammation

Cluster: FA00.Z&XK8G/MG30.30

How Do ICD-11 Codes Compare to ICD-9 and ICD-10?

Here are two examples of how ICD codes have evolved over time. Note that the examples show the ICD-9-CM and ICD-10-CM codes used in the United States. The ICD-11 codes are from the January 2026 version of the ICD-11 Coding Tool.

1) Essential hypertension, unspecified:

ICD-9-CM 2015: 401.9 Unspecified essential hypertension

ICD-10-CM 2026: I10 Essential (primary) hypertension

ICD-11: BA00.Z Essential hypertension, unspecified

2) Diabetes mellitus, type 2, with left diabetic cataract:

ICD-9-CM 2015: 250.50 Diabetes with ophthalmic manifestations, type II or unspecified type, not stated as uncontrolled, and 366.41 Diabetic cataract

ICD-10-CM 2026: E11.36 Type 2 diabetes mellitus with diabetic cataract

ICD-11: 5A11/9B10.21&XK8G

5A11 Type 2 diabetes mellitus

9B10.21 Diabetic cataract

XK8G Left

Advantages of ICD-11

After the tumultuous, years-long transition to ICD-10-CM, simply mentioning ICD-11 may produce stress for revenue cycle professionals and healthcare providers across the United States. Examining the major concepts included in the 11th revision, as well as implementation considerations, may help remove some of that anxiety.

Let’s start with some key changes and the advantages of ICD-11:

Easy to use:

• The coding system is more contemporary and more easily integrated with electronic health records than past versions.

• ICD-11 is designed for digital use and integration with electronic health information systems, while also supporting use in paper-based settings. Resources include the online Coding Tool, Implementation or Transition Guide, Reference Guide, and Browser, all available on WHO’s ICD-11 page.

Greater digital capabilities:

• ICD-11’s digital format enables it to be continuously updated, improves coordination with other classifications and terminologies, provides flexibility to reduce the need for clinical modifications, and improves the comparability of translations.

• ICD-11 is designed to be computable and supports computer-assisted and automated coding from clinical documentation.

Updated structure and current scientific content:

• A reformulated chapter structure and indexing system require relocation of some existing codes.

• Besides diseases, ICD-11 includes external causes, disorders, signs and symptoms, anatomy, histopathology, and much more.

• ICD-11 uses a new alphanumeric code structure. Stem codes are based on four-character category codes and may include additional characters after a decimal point; extension codes begin with X. The available, potential stem-code range extends from 1A00.00 to ZZ9Z.ZZ.

Improvements:

• ICD-11 reorganizes and expands the classification to reflect current medical knowledge. New or substantially revised areas include diseases of the immune system, sleep-wake disorders, conditions related to sexual health, and developmental anomalies. ICD-11 also includes supplementary content for functioning assessment and the optional recording of traditional medicine conditions.

• ICD-11 allows multiple applications to meet health system priorities. Examples include mortality, morbidity, primary care reporting, clinical recording, research, patient safety, antimicrobial resistance, epidemiology, population health, health system performance, resource allocation, and reimbursement.

Better coding quality:

• ICD-11 enables more straightforward coding. Simple coding can be done as well as coding of complex clinical detail.

• The introduction of extensions and clustering allows for the addition of specific detail to coded entities.

• The new coding structure provides greater flexibility than previous versions by allowing codes to be combined, where permitted, to represent additional clinical detail.

How Will the U.S. Implement ICD-11?

Countries are transitioning to ICD-11 according to their individual needs, resources, and implementation plans, so the timing of adoption varies internationally. There is no U.S. implementation date for ICD-11 morbidity coding. As of August 2026, the U.S. continues to use ICD-10 for mortality reporting and ICD-10-CM for morbidity coding.

In contrast to mortality, coding for morbidity (sickness, injury, disability) has evolved in a divergent manner at the national level in response to emerging needs and local practices in healthcare provision. In the countries where this has occurred, the transition to ICD-11 may require a tailored approach to allow for these differences in reporting rules and coding, but the goal is to ultimately transition toward an internationally consistent output.

WHO recognizes that countries may require adaptations of ICD-11 for particular healthcare settings or reimbursement needs. ICD-11’s flexibility is intended to minimize the need for divergent national modifications and preserve international comparability.

The National Committee on Vital and Health Statistics (NCVHS) has evaluated issues related to potential ICD-11 implementation for morbidity coding in the U.S. In 2024, NCVHS recommended that the Department of Health & Human Services (HHS) designate a federal office or agency to coordinate ICD-11 morbidity coding activities in the United States, including research, funding, rulemaking, and resources related to adoption, implementation, and maintenance. NCVHS also recommended appointing a federal representative to participate in WHO activities related to morbidity coding while that coordinating structure is being established.

New Concepts Included in ICD-11

Below are some of the main areas and concepts developed and used in ICD-11.

• ICD-11 includes concepts for recording and reporting health information in primary care and can also be used in specialist and highly specialized healthcare settings.

• ICD-11 provides more detailed coding for patient safety events, supporting standardized documentation and analysis of quality and patient safety.

• ICD-11 includes specific coding for antimicrobial resistance, supporting more precise documentation and analysis and alignment with the WHO Global Antimicrobial Resistance and Use Surveillance System (GLASS).

• ICD-11 provides more detailed classification of HIV disease, including specific coding for clinical stages and improved ability to document HIV together with associated diseases and complications.

• A supplementary functioning section allows functional status to be assessed and monitored. It includes the WHO Disability Assessment Schedule 2.0 (WHODAS 2.0) for documenting functioning across different areas of daily life.

• ICD-11 includes about 5,500 rare diseases and their synonyms, with regular updates in collaboration with Orphanet. Every rare disease represented in the ICD-11 Foundation has a unique Uniform Resource Identifier (URI), although only some have an individual statistical code. URIs allow rare diseases to be identified individually and support detailed documentation and interoperability with other health information systems.

• The supplementary chapter for traditional medicine conditions provides standardized categories for optional dual coding alongside diagnoses from the main ICD-11 chapters. It supports consistent documentation and international comparison and includes East Asian traditional medicine conditions as well as a module covering Ayurveda and related systems, including Siddha and Unani.

What Does the Future Hold?

Like past ICD versions, ICD-11 has the potential to greatly impact the provision of care, health financing, and resource allocation. The increased detail and flexibility built into ICD-11, coupled with its electronic format, will help it to serve as a living document for many purposes, ensuring its longevity.

It would be premature to speculate when the U.S. will be prepared to transition to ICD-11 or whether a U.S. clinical modification will be necessary, as occurred with ICD-9 and ICD-10. Though timing and many other details remain uncertain, U.S. policy and planning discussions related to an eventual transition to ICD-11 are underway.

ICD-11 is looming large on the healthcare horizon. Once a U.S. implementation approach and timeline are established, practices will need adequate preparation, including updates to systems, workflows, documentation processes, and coder education, to minimize potential disruption to coding and reimbursement. It’s imperative to monitor ICD-11 planning and keep an eye on any developments to ensure your practice is equipped for a smooth and efficient implementation of ICD-11.

Last reviewed on Aug. 10, 2026, by the AAPC Thought Leadership Team