ICD-10 G21.0
Billable / Specific MCCMalignant neuroleptic syndrome
About ICD-10-CM G21.0
ICD-10-CM code G21.0 represents Malignant neuroleptic syndrome. This is a billable/specific code in the Nervous System chapter (block G21). The 2026 edition of ICD-10-CM G21.0 became effective on October 1, 2025.
Coding Tips for G21.0
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
G21.0 is designated MCC for MS-DRG grouping. On inpatient claims, this code can shift the DRG to the with-MCC variant when documented as a present-on-admission secondary diagnosis. Hospital CDI programs flag MCC opportunities during chart review. Failure to capture this code may leave 30 to 80 percent of the inpatient stay revenue unrealized.
Type 1 Excludes
Pure excludes, these codes can never be coded together with G21.0. The conditions are mutually exclusive (e.g., congenital vs acquired forms).
- neuroleptic induced parkinsonism (G21.11)
Use Additional Code
When coding G21.0, also report these additional codes when applicable.
- code for adverse effect, if applicable, to identify drug (T43.3X5, T43.4X5, T43.505, T43.595)
Inpatient DRG Impact, MCC
codes Malignant neuroleptic syndrome. As a Major Complication/Comorbidity (MCC), this can shift the DRG assignment to a higher-weighted category, substantial reimbursement impact.
Medicare LCD Coverage for G21.0
Local Coverage Determinations (LCDs) from CMS MACs that list G21.0 as a covered diagnosis.
Showing top 10 of 292 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing G21.0.
4 Aetna
5 Medicare
CPT Codes Commonly Billed with G21.0
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- 92571 CMS LCD: Billing and Coding: Vestibular and Audiologic Function Studies CMS LCD
- 92568 CMS LCD: Billing and Coding: Vestibular and Audiologic Function Studies CMS LCD
- 92620 CMS LCD: Billing and Coding: Vestibular and Audiologic Function Studies CMS LCD
- 92588 CMS LCD: Billing and Coding: Vestibular and Audiologic Function Studies CMS LCD
- 92572 CMS LCD: Billing and Coding: Vestibular and Audiologic Function Studies CMS LCD
- 92579 CMS LCD: Billing and Coding: Vestibular and Audiologic Function Studies CMS LCD
- 92582 CMS LCD: Billing and Coding: Vestibular and Audiologic Function Studies CMS LCD
- 92576 CMS LCD: Billing and Coding: Vestibular and Audiologic Function Studies CMS LCD
- 92621 CMS LCD: Billing and Coding: Vestibular and Audiologic Function Studies CMS LCD
- 92570 CMS LCD: Billing and Coding: Vestibular and Audiologic Function Studies CMS LCD
Convert G21.0 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| G21.0 | 33392 | 00000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To G21.0
Other codes in section G20-G26 (Extrapyramidal and movement disorders).
ICD-10 G21.0, Billing FAQ
Is ICD-10 code G21.0 billable? +
Yes, G21.0 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What codes are Type 1 Excludes for G21.0? +
Type 1 Excludes (never code together with G21.0): neuroleptic induced parkinsonism (G21.11)
Is G21.0 a CC or MCC for inpatient DRG? +
Yes, this code is designated as MCC. Documenting as a secondary diagnosis on inpatient claims can shift the DRG to a higher-weighted category.
What CPT codes are commonly billed with G21.0? +
Procedures frequently paired with G21.0 include: 92571, 92568, 92620, 92588, 92572.
What ICD-9 codes does G21.0 map to? +
Per CMS GEMs, G21.0 maps to ICD-9 codes: 33392. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on July 16, 2026.
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