Learn to Code: Alzheimer’s Disease

5 min read

Did you know? June is Alzheimer’s & Brain Awareness Month. Read more to learn about Alzheimer’s disease, how it is categorized in ICD-10-CM, and how it relates to dementia.

What Is Alzheimer's Disease?

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Alzheimer’s disease is a process of progressive atrophy involving the degeneration of nerve cells. This degeneration leads to mental changes that range from subtle intellectual impairment to dementia with loss of cognitive functions and failure of memory. Alzheimer’s is a progressive disease, meaning it gets worse over time. According to the Alzheimer’s Association, “a person with Alzheimer’s lives four to eight years after diagnosis but can live as long as 20 years.”  

The disease was first described in 1906 by a German physician named Dr. Alois Alzheimer. Dr. Alzheimer encountered a patient named Auguste D. who presented with symptoms of profound memory loss, hallucinations, and disorientation. After Auguste died at the age of 50, Dr. Alzheimer conducted a post-mortem autopsy and discovered various abnormalities in her brain. According to Alzheimer’s Disease International, “[Auguste’s] cerebral cortex was thinner than normal and senile plaque...was found in the brain along with neurofibrillary tangles.” 

Dr. Alzheimer presented his findings on his patient during a speech at the 37th Congress of Psychiatrists of Southern Germany in 1906. He depicted Auguste’s symptoms as “a unusual disease of the cerebral cortex.”  Dr. Alzheimer’s colleague, Dr. Emil Kraepelin, named the disease after its discoverer in the 8th edition of Handbook of Psychiatry (1910). Over 100 years later, as Alzheimer’s Disease International notes, “the pathological diagnosis of Alzheimer’s disease is still generally based on the same investigative methods used in 1906.”  

How Is Alzheimer’s Disease Categorized in ICD-10-CM?

Alzheimer’s Disease is classified as a disease of the nervous system in chapter 6 of ICD-10-CM. It is a disease that affects the central nervous system. It is coded to category G30 and further subdivided to specify the type of Alzheimer’s Disease.  

What Are the Different Types of Alzheimer’s Disease?  

While clinicians may also document the stage of the disease as either early/mild, middle/moderate, or late/severe, these stages correlate to the severity of dementia that is a manifestation of Alzheimer’s disease. ICD-10-CM only includes subcategories for G30 to specify when the disease began, if known: early onset or late onset. If the onset is not specified, then the disease is classified as either other or unspecified. Remember that medical coding professionals can only assign codes based on the provider’s documentation of the condition.  

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Early Onset  

Early onset Alzheimer’s is also known as younger-onset Alzheimer’s. The disease is considered early onset if it affects a person younger than 65 years old.  

Late Onset  

Late onset Alzheimer’s typically appears in patients older than 65 years old.  

Other

Other Alzheimer’s is some other type of the disease that is documented by the provider that is neither early onset or late onset. For example, if a provider describes the condition as mild, moderate, or severe, but does not specify early onset or late onset, the condition code assigned would be “Alzheimer’s, Other.”  

Unspecified

Unspecified Alzheimer’s is assigned when the condition is neither documented as late or early onset nor mild, moderate, or severe. In this scenario, the condition is simply documented as Alzheimer’s disease.  

What About Dementia?

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Dementia is a general term for memory loss and other cognitive abilities that seriously affect daily life; dementia is also an inherent part of Alzheimer’s disease. The provider does not need to document the condition separately for a patient with Alzheimer’s disease. The 1st Quarter 2017 Coding Clinic for ICD-10-CM and ICD-10-PCS addressed this question of when two codes are required for a patient diagnosed with Alzheimer’s disease. As the AHA Central Office explained, the Official Guidelines for Coding and Reporting pertaining to the etiology/manifestation convention (1.A.13), states “Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the ICD-10-CM has a coding convention that requires the underlying condition be sequenced first, if applicable, followed by the manifestation. Wherever such a combination exists, there is a “use additional code” note at the etiology code, and a “code first” note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes, etiology followed by manifestation.”

Conclusion

Alzheimer’s is the most common cause of dementia and causes problems with memory, thinking, and behavior. While it cannot be cured, there are treatments available and ongoing research to develop new treatments.

For more information about Alzheimer’s Disease, please visit the Alzheimer’s Association’s website. For more detailed information about how to code Alzheimer’s disease, please read chapter 17 of the ICD-10-CM and ICD-10-PCS Coding Handbook or look up content published in AHA Coding Clinic for ICD-10-CM and ICD-10-PCS on our enhanced search.  

Resources

1. AHA Coding Clinic for ICD-10-CM and ICD-10-PCS. (2017, March 13). AHA Coding Clinic Advisor. Retrieved June 2, 2025, from https://www.codingclinicadvisor.com/library/icd10/2017/first/aha-coding-clinic-icd-10-q1-2017# target="_blank".  
2. American Hospital Association. (2024). Chapter 17, Alzheimer’s Disease. In ICD-10-CM and ICD-10-PCS Coding Handbook 2025, With Answers (2025th ed., p. 214).  
3. What is Alzheimer’s Disease? Alzheimer’s Association. (n.d.). https://www.alz.org/alzheimers-dementia/what-is-alzheimers#basics
4. Who is Alois Alzheimer? Alzheimer’s Disease International (ADI). (n.d.). https://www.alzint.org/about/dementia-facts-figures/types-of-dementia/alzheimers-disease/alois-alzheimer/
5. U.S. Centers for Medicare & Medicaid Services. (n.d.). ICD-10-CM Tabular list of Diseases and Injuries. CMS.gov. https://www.cms.gov/medicare/coding/icd10/downloads/6_i10tab2010.pdf