ICD-10 G40.109
Billable / Specific HCC v28: 79 CCLocalization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures, not intractable, without status epilepticus
About ICD-10-CM G40.109
ICD-10-CM code G40.109 represents Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures, not intractable, without status epilepticus. This is a billable/specific code in the Nervous System chapter (block G40). The 2026 edition of ICD-10-CM G40.109 became effective on October 1, 2025.
Coding Tips for G40.109
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
G40.109 is a CMS-HCC v28 risk-adjustment code (category 79). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
G40.109 is designated CC for MS-DRG grouping. On inpatient claims, this code can shift the DRG to the with-CC variant when documented as a present-on-admission secondary diagnosis. Hospital CDI programs flag CC opportunities during chart review. Failure to capture this code may leave 30 to 80 percent of the inpatient stay revenue unrealized.
Inclusion Terms / Approximate Synonyms
Clinical terms and conditions classified under G40.109. Per CMS ICD-10-CM Tabular 2026.
- Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures NOS
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Inpatient DRG Impact, CC
codes Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures, not intractable, without status epilepticus. As a Complication/Comorbidity (CC), this contributes to DRG severity adjustment when documented alongside the principal diagnosis.
Medicare LCD Coverage for G40.109
Local Coverage Determinations (LCDs) from CMS MACs that list G40.109 as a covered diagnosis.
Showing top 10 of 463 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing G40.109.
3 Cigna
5 Medicare
CPT Codes Commonly Billed with G40.109
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- 95708 CMS LCD: Billing and Coding: Special Electroencephalography CMS LCD
- 95721 CMS LCD: Billing and Coding: Special Electroencephalography CMS LCD
- 95719 CMS LCD: Billing and Coding: Special Electroencephalography CMS LCD
- 95813 CMS LCD: Billing and Coding: Special Electroencephalography CMS LCD
- 95822 CMS LCD: Billing and Coding: Special Electroencephalography CMS LCD
- 95717 CMS LCD: Billing and Coding: Special Electroencephalography CMS LCD
- 95812 CMS LCD: Billing and Coding: Special Electroencephalography CMS LCD
- 95700 CMS LCD: Billing and Coding: Special Electroencephalography CMS LCD
- 95705 CMS LCD: Billing and Coding: Special Electroencephalography CMS LCD
- 95711 CMS LCD: Billing and Coding: EEG � Ambulatory Monitoring CMS LCD
Convert G40.109 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 |
|---|---|---|
| G40.109 | 34550 | 10000 |
| G40.109 | 34570 | 10000 |
| G40.109 | 34580 | 10000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To G40.109
Other codes in section G40-G47 (Episodic and paroxysmal disorders).
ICD-10 G40.109, Billing FAQ
Is ICD-10 code G40.109 billable? +
Yes, G40.109 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What other names or terms map to G40.109? +
ICD-10 G40.109 includes: Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures NOS.
Does G40.109 affect Medicare Advantage HCC risk adjustment? +
Yes. G40.109 maps to CMS-HCC v28 category 79. Capture this diagnosis annually for accurate Medicare Advantage risk score.
Is G40.109 a CC or MCC for inpatient DRG? +
Yes, this code is designated as CC. Documenting as a secondary diagnosis on inpatient claims can shift the DRG to a higher-weighted category.
What CPT codes are commonly billed with G40.109? +
Procedures frequently paired with G40.109 include: 95708, 95721, 95719, 95813, 95822.
What ICD-9 codes does G40.109 map to? +
Per CMS GEMs, G40.109 maps to ICD-9 codes: 34550, 34570, 34580. 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 June 1, 2026.
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