ICD-10 Parkinson’s: All G20, G21, G22 & F Codes with Updates

The International Classification of Diseases, 10th Revision (ICD-10), is a globally recognized system used to classify and code diseases, symptoms, and medical conditions. It provides a standardized language that helps healthcare professionals accurately document diagnoses, track disease statistics, and facilitate billing and insurance processes worldwide.

Within this system, Parkinson’s disease is primarily represented by the ICD-10 code G20, though the exact usage may vary slightly depending on the version applied.

For WHO coding of Parkinson’s disease, ICD-10 code is G20, which covers all forms of the disease, whether with or without dementia, with or without dyskinesia, or unspecified cases.

In the US ICD-10-CM, subcodes like G20.A (without dyskinesia) and G20.B (with dyskinesia) exist, while supplementary codes such as F02.80 or F02.81 can document dementia or behavioral disturbances.

In this article, we will explore the ICD-10 coding for Parkinson’s disease, including distinctions between primary and secondary forms, and how clinical features like dyskinesia, motor fluctuations, or dementia are documented.

Importance of ICD-10 Coding for Parkinson’s Disease

1. Recognizing the ICD-10 coding is essential for Parkinson’s disease because it standardizes clinical documentation, improves communication among healthcare providers, and ensures accurate billing and insurance claims.

2. Beyond general documentation, coding allows clinicians to differentiate between types of Parkinsonism, such as primary Parkinson’s disease, secondary Parkinsonism, or Parkinsonism associated with other conditions.

3. It prevents errors that could lead to misleading documentation, such as confusing primary Parkinson’s disease (G20) with secondary Parkinsonism (G21), which may result in misdiagnosis or inappropriate treatment.

4. This distinction is crucial for tailoring treatment plans, tracking disease progression, and managing complications like dyskinesia.

5. Accurate coding also enables the collection of reliable data for research, epidemiology, and quality-of-care evaluations, ultimately supporting better patient outcomes.

Parkinson’s ICD-10 Differ by Coding Systems (CMS & WHO)

Both the World Health Organization (WHO) and the Centers for Medicare & Medicaid Services (CMS) provide guidelines to ensure consistent coding practices.

Parkinson’s disease (PD) coding differs between the WHO’s ICD-10 and the US ICD-10-CM (used by CMS). The WHO ICD-10 uses a single, general code (G20), which is simpler to apply but does not allow documentation of motor complications such as dyskinesia or “off” episodes—important factors for tracking disease progression.

In contrast, the US ICD-10-CM employs a more detailed system with multiple subcodes to capture specific clinical features, including the presence or absence of dyskinesia and motor fluctuations, providing more precise information for patient management and reporting.

What is the ICD-10 code for Parkinson's disease?

The ICD-10 code for Parkinson’s disease is G20, which is the single code used in the WHO classification.

It covers all forms of Parkinson’s disease, regardless of associated symptoms such as dementia or dyskinesia, and does not have subcodes or extensions based on disease variations, unlike many other neurological disorders.

In contrast, the US ICD-10-CM (Clinical Modification) provides additional subcodes to differentiate and subdivide Parkinsonism depending on symptoms associated, such as G20.A for Parkinson's disease without dyskinesia and G20.B for Parkinson’s disease with dyskinesia

ICD-10 for Unspecified Parkinson’s Disease

Unspecified or typical Parkinson’s disease is likewise included under G20. Since the definition of the disease already implies an unspecified type, no additional subcodes are needed unless the condition is secondary or drug-induced, in which case other codes may apply.

ICD-10 for Parkinson’s Disease With Dementia (PDD)

Parkinson’s disease with dementia is still coded under G20 in ICD-10, as there are no separate subcodes for dementia in the WHO version. In the US ICD-10-CM system, supplementary codes such as F02.80 and for dementia in other diseases or F02.81 for dementia with behavioral disturbance may be used to document cognitive or behavioral symptoms beside the G20 code for parkinson.

ICD-10 for Parkinson’s Disease With Dyskinesia

In the US ICD-10-CM system (used by the Centers for Medicare & Medicaid Services, CMS), Parkinson’s disease with dyskinesia is coded as G20.B1 for cases without motor fluctuations and G20.B2 for cases with motor fluctuations.

In contrast, the WHO ICD-10 system does not provide separate subcodes for dyskinesia; all cases of Parkinson’s disease with or without dyskinesia are coded simply as G20.

ICD-10 for Parkinson’s Disease Without Dyskinesia

In the US ICD-10-CM system, Parkinson’s disease without dyskinesia is coded as G20.A1 for cases without motor fluctuations and G20.A2 for cases with motor fluctuations. If the presence or absence of fluctuations is not specified, the broader code G20.A may be used.

In contrast, the WHO ICD-10 system does not distinguish between dyskinesia or fluctuations—all cases of Parkinson’s disease, with or without dyskinesia, are coded simply as G20.

ICD-10 for Primary vs. Secondary Parkinson’s Disease

Primary coding rules use G20 for idiopathic, or primary, Parkinson’s disease, which should be listed as the first diagnosis.

Secondary coding rules apply to Parkinsonism caused by another condition, such as drug-induced Parkinsonism or Parkinsonism with an unspecified cause.

In these cases, the underlying pathology is different from primary Parkinson’s and may not involve the dopaminergic pathway.

G20 is not used for secondary Parkinsonism; instead, only the specific symptoms or related conditions are coded, such as dementia (F02.80/F02.81) or dyskinesia (using additional ICD-10-CM symptom codes).

ICD-10 Codes for Primary Parkinson’s Disease

ICD-10 Codes for Secondary Parkinson’s Disease (Parkinsonism)

Differences Between ICD-10 G20, G21, and G22 Codes

The primary difference is that G20 is for Parkinson's disease, G21 is for secondary Parkinsonism caused by other factors like medication, and G22 is for Parkinsonism that occurs as a result of a different, classified disease.

1. G20 – Parkinson’s Disease: This is the primary code used for idiopathic Parkinson’s disease, covering all forms of the disease regardless of symptom variations such as dementia or dyskinesia. In the WHO ICD-10 version, there are no subcodes or extensions, and all additional features are documented using supplementary codes if needed.

1. G21 – Secondary Parkinsonism: This code is used for Parkinsonism that arises due to external or identifiable factors, such as medication, toxins, or other medical conditions. Subcategories under G21 (e.g., G21.0, G21.1) allow clinicians to specify the exact cause, helping with accurate documentation, research, and treatment planning.

1. G22 – Parkinsonism in Diseases Classified Elsewhere: This code is applied when Parkinsonian symptoms occur as part of another underlying disease that is classified in a different section of ICD-10, such as a neurodegenerative or metabolic disorder. Using G22 ensures that Parkinsonism is correctly linked to its primary condition while maintaining proper coding hierarchy.

ICD-10 vs ICD-11 Coding for Parkinson’s Disease

ICD-11 introduces a more specific and detailed coding system for Parkinson’s disease compared to ICD-10. While ICD-10 uses a single code (G20) for all forms of Parkinson’s disease, ICD-11 adopts a hierarchical structure that differentiates between primary Parkinson’s disease (8A00.0), atypical Parkinsonism (8A00.1), and secondary Parkinsonism (8A00.2).

ICD-11 also updates terminology and subcategories, allowing clinicians to capture nuances such as disease type, severity, and associated manifestations, which improves coding precision and the quality of clinical data for research and treatment planning.

Despite these improvements, ICD-10 remains the standard in most healthcare systems worldwide due to its long-standing integration in electronic health records, insurance, and billing processes; transitioning to ICD-11 requires software updates, coder training, and widespread adoption.

Common Coding Errors to Avoid

Even experienced coders can make mistakes when documenting Parkinson’s disease. Common errors include:

1. Using separate codes for features already covered under G20 in WHO ICD-10.
2. Confusing secondary Parkinsonism (G21) with primary Parkinson’s disease (G20).
3. Omitting supplementary codes for dementia or behavioral disturbances when required in ICD-10-CM.
4. Incorrectly assuming that dyskinesia is a subcode of G20 in the WHO ICD-10.

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