ICD-10 Code G30.9: Alzheimer’s Disease, Unspecified

Key Takeaways

G30.9 is the ICD-10-CM code for Alzheimer’s disease, unspecified, when onset type cannot be determined from documentation

G30.9 must always be paired with a secondary F02.xx dementia code per the ICD-10-CM “Code Also” instructional note

The default pairing is G30.9 + F02.80 (no behavioral disturbance); add behavioral specifier subcodes when documentation supports them

Pabau’s claims management tools help neurology and memory care practices apply dual-coding rules accurately and reduce denials

ICD-10 Code G30.9: Definition and Clinical Description

Most Alzheimer’s disease claims arrive at the payer with the wrong secondary code, or no secondary code at all. That single documentation gap triggers denials that could be avoided with a clear understanding of ICD-10 Code G30.9 and its mandatory pairing rules. This reference covers everything coders and clinicians at memory care practices need: code definition, when G30.9 applies versus its sibling codes, how to apply the F02.xx dual-coding requirement correctly, and what documentation must support each specifier.

ICD-10 Code G30.9 classifies Alzheimer’s disease when clinical documentation does not specify an onset type. It sits within the G30 category (Alzheimer’s disease) under Chapter 6 of ICD-10-CM, covering diseases of the nervous system. The CDC/NCHS ICD-10-CM web tool confirms G30.9 as a billable, specific code valid for reimbursement purposes across all payer types including Medicare, Medicaid, and commercial insurers.

Alzheimer’s disease is characterized by progressive neurodegeneration involving amyloid plaques and neurofibrillary tangles that destroy cortical neurons over time. Clinically, it presents as a major neurocognitive disorder with memory impairment, executive dysfunction, and, in later stages, loss of activities of daily living. The ICD-10-CM coding system separates the underlying disease (G30 category) from the dementia manifestation it causes (F02 category), which is why every G30.9 claim requires a paired F02.xx code.

Synonyms included under G30.9 per the ICD-10-CM index include: Alzheimer’s disease NOS (not otherwise specified), Alzheimer’s dementia NOS, and senile dementia with Alzheimer’s type. Senility NOS, however, maps to R41.81 and is excluded from the G30 category entirely.

G30 Subcategory Breakdown: Choosing the Right Code

Before assigning G30.9, verify the provider’s documentation for any onset description. The G30 category offers four codes, and selecting an unspecified code when a more specific one is supportable will generate a Yoast-style “specificity” flag from many clearinghouses and can attract payer audit attention.

The AAPC Codify ICD-10-CM reference notes that G30.0 and G30.1 are defined by patient age at symptom onset, not at diagnosis. A patient first diagnosed at age 72 with documented onset of symptoms at age 58 would qualify for G30.0, not G30.1. When the record is silent on onset, G30.9 is the appropriate choice. Coders working within a psychiatry EMR or memory care setting should build a query workflow to prompt providers for onset documentation before the encounter closes.

Dual Coding: G30.9 and the Required F02.xx Pairing

This is where most Alzheimer’s coding errors occur. The ICD-10-CM tabular list includes a “Code Also” instructional note at G30.9 requiring coders to assign an additional code for any associated dementia. Omitting this second code produces an incomplete claim that many payers will reject or suspend for medical review.

The F02 code category covers major neurocognitive disorder due to Alzheimer’s disease. In FY2026, these codes are structured by severity and behavioral disturbance specifiers. The default combination when documentation is silent on behavioral symptoms is:

• G30.9 (sequenced first, as the underlying disease)
• F02.80 (major neurocognitive disorder due to Alzheimer’s disease, unspecified severity, without behavioral disturbance, sequenced second)

Sequencing matters. Per ICD-10-CM Official Guidelines, G30.9 is always the principal or first-listed code when Alzheimer’s disease is the condition driving the encounter. F02.xx follows as an additional diagnosis. Reversing the sequence is a coding error that can affect DRG assignment in inpatient settings and E/M medical necessity review in outpatient settings. Practices using claims management software can apply edit rules to flag reversed Alzheimer’s code pairs before submission.

According to the CMS ICD-10-CM coding resources, the “Code Also” instruction applies to all G30.x codes, not just G30.9. Practices seeing patients across the onset spectrum should apply the same dual-coding rule regardless of whether they use G30.0, G30.1, G30.8, or G30.9.

Behavioral Disturbance Specifiers and ICD-10 Code G30.9

When a patient with Alzheimer’s disease presents with documented behavioral symptoms, coders must select an F02 subcode that captures the specific behavioral disturbance. The FY2026 ICD-10-CM F02 code set uses an expanded specifier structure beyond the older F02.80/F02.81 split. Assigning F02.80 for a patient with documented agitation is a specificity downcode that payers may flag during claims review.

The behavioral disturbance specifier series applicable to Alzheimer’s-related dementia includes categories for mood symptoms, psychotic features, agitation/aggression, and other specified disturbances. Because specific F02 subcode designations within the F02.A, F02.B, and F02.C series are updated annually, coders should verify the current FY2026 ICD-10-CM tabular list before assignment. The CDC ICD-10-CM web tool provides year-specific lookups to confirm active codes.

Practical guidance for determining the correct behavioral specifier:

• No behavioral symptoms documented: Use F02.80 (unspecified severity, without behavioral disturbance)
• Agitation or aggression documented: Use the applicable F02.C-series subcode for agitation; verify exact subcode in the FY2026 tabular
• Mood symptoms (anxiety, depression) documented: Use the applicable F02.A-series subcode
• Psychotic features (hallucinations, delusions) documented: Use the applicable F02.B-series subcode

The behavioral specifier must be supported by specific clinical language in the encounter note. A vague notation of “patient appears agitated” may not satisfy payer requirements; documentation should reflect the provider’s clinical assessment of the behavioral feature and its relationship to the Alzheimer’s diagnosis. Structured digital forms built around the F02 specifier matrix help providers capture the right language at the point of care.

Documentation Requirements for G30.9 Coding Accuracy

Payers auditing Alzheimer’s disease claims look for three documentation elements: a confirmed diagnosis, an onset or type indicator (or a clear statement that onset is unknown), and a clinical basis for any behavioral specifier assigned. Missing any of these creates an audit exposure risk, particularly for Medicare Advantage plans that apply hierarchical condition category (HCC) risk adjustment to dementia codes.

G30.9 versus F03.90 is the most common coding confusion in outpatient memory care. F03.90 represents unspecified dementia of unspecified severity without behavioral disturbance, while G30.9 + F02.80 represents Alzheimer’s disease with associated dementia. If the provider has documented a specific diagnosis of Alzheimer’s disease, regardless of onset type, G30.9 is the correct disease code. F03.90 applies only when the type of dementia is genuinely unknown or cannot be determined even after clinical evaluation. Using F03.90 for a confirmed Alzheimer’s patient is a coding error, not a conservative choice.

The client record should capture the following to support a G30.9 claim:

• A documented diagnosis of Alzheimer’s disease (or Alzheimer’s dementia) from the provider
• A statement on behavioral symptoms present or absent (to justify F02.8x vs. F02.A/B/C-series)
• A statement on disease severity if documented (mild, moderate, or severe stage)
• Documentation that onset type is unknown or unspecified if G30.9 is being used over G30.0 or G30.1

Memory care practices and neurology groups using a mental health EMR can configure note templates to prompt for each of these documentation elements at the close of every Alzheimer’s-related encounter. This reduces the need for coder queries after the fact and supports cleaner first-pass claim submissions.

Reduce Alzheimer’s Coding Denials with Pabau

Pabau's claims management tools help neurology and memory care practices apply ICD-10-CM dual-coding rules accurately. Build structured note templates, track claim outcomes, and reduce preventable denials from incomplete G30.9 pairings.

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Additional Coding Considerations: Crosswalk, Exclusions, and Related Codes

Coders transitioning older records or handling continuity-of-care documentation may encounter ICD-9-CM codes that require crosswalk mapping. The ICD-9-CM equivalent for G30.9 is 331.0 (Alzheimer’s disease). Per ICD-10-CM crosswalk guidance from the Research Data Assistance Center (ResDAC), approximate conversions between ICD-9-CM and ICD-10-CM codes may require clinical interpretation. The mapping is not always one-to-one, and ICD-9-CM 331.0 did not carry the same mandatory dual-coding requirement that G30.9 carries under ICD-10-CM.

Several codes in neighboring categories are worth distinguishing from G30.9:

• G31.9 (Degenerative disease of nervous system, unspecified): Used for neurodegeneration when Alzheimer’s disease is not confirmed; excluded from the G30 category
• F03.90 (Unspecified dementia, unspecified severity, without behavioral disturbance): Used when dementia type cannot be determined; not appropriate for confirmed Alzheimer’s patients
• R41.81 (Age-related cognitive decline, senility NOS): Excluded from G30 category; used for cognitive changes not meeting dementia criteria

The compliance management software workflows in Pabau can be configured to flag these common substitution errors during pre-submission claim review, catching cases where F03.90 or R41.81 has been applied to a record carrying a confirmed Alzheimer’s diagnosis in the problem list.

Expert Resources for G30.9 Coding and Dementia Documentation

Expert Picks

Need to document Alzheimer’s behavioral symptoms at scale? Digital Forms lets memory care teams build structured encounter templates that capture F02 specifier criteria at the point of care.

Looking for an EMR built for psychiatric and cognitive care workflows? Psychiatry EMR Software covers documentation, scheduling, and claims in one platform.

Want to reduce Alzheimer’s coding denials before they reach the payer? Claims Management Software applies pre-submission edits to catch missing F02.xx pairings and sequencing errors.

Managing compliance across a multi-provider memory care group? Compliance Management Software helps practice managers track documentation standards and audit readiness.

Conclusion

Alzheimer’s disease coding fails at the dual-coding step more than any other point. G30.9 without a paired F02.xx is an incomplete claim regardless of how accurate the primary code is. The default pairing is G30.9 + F02.80, but when behavioral disturbances are documented, the F02 specifier must reflect them specifically.

Pabau’s claims management tools help memory care and neurology practices build the edit rules and note templates that catch these gaps before claims leave the practice. To see how Pabau handles Alzheimer’s coding workflows in a live environment, book a demo with the team.

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