ICD-10 G40.309
Billable / Specific HCC v28: 79Generalized idiopathic epilepsy and epileptic syndromes, not intractable, without status epilepticus
About ICD-10-CM G40.309
ICD-10-CM code G40.309 represents Generalized idiopathic epilepsy and epileptic syndromes, 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 G40.309 became effective on October 1, 2025.
Coding Tips for G40.309
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
G40.309 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.
Inclusion Terms / Approximate Synonyms
Clinical terms and conditions classified under G40.309. Per CMS ICD-10-CM Tabular 2026.
- Generalized idiopathic epilepsy and epileptic syndromes 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.
Medicare LCD Coverage for G40.309
Local Coverage Determinations (LCDs) from CMS MACs that list G40.309 as a covered diagnosis.
Showing top 10 of 571 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing G40.309.
3 Cigna
5 Medicare
CPT Codes Commonly Billed with G40.309
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- G0480 CMS LCD: Billing and Coding: Urine Drug Testing CMS LCD
- 80306 CMS LCD: Billing and Coding: Urine Drug Testing CMS LCD
- G0482 CMS LCD: Billing and Coding: Urine Drug Testing CMS LCD
- 0603U CMS LCD: Billing and Coding: Urine Drug Testing CMS LCD
- 80305 CMS LCD: Billing and Coding: Urine Drug Testing CMS LCD
- G0659 CMS LCD: Billing and Coding: Urine Drug Testing CMS LCD
- G0483 CMS LCD: Billing and Coding: Urine Drug Testing CMS LCD
- 80307 CMS LCD: Billing and Coding: Urine Drug Testing CMS LCD
- G0481 CMS LCD: Billing and Coding: Urine Drug Testing CMS LCD
- 95711 CMS LCD: Billing and Coding: EEG � Ambulatory Monitoring CMS LCD
Convert G40.309 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 |
|---|---|---|
| G40.309 | 34510 | 10000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To G40.309
Other codes in section G40-G47 (Episodic and paroxysmal disorders).
ICD-10 G40.309, Billing FAQ
Is ICD-10 code G40.309 billable? +
Yes, G40.309 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 G40.309? +
ICD-10 G40.309 includes: Generalized idiopathic epilepsy and epileptic syndromes NOS.
Does G40.309 affect Medicare Advantage HCC risk adjustment? +
Yes. G40.309 maps to CMS-HCC v28 category 79. Capture this diagnosis annually for accurate Medicare Advantage risk score.
What CPT codes are commonly billed with G40.309? +
Procedures frequently paired with G40.309 include: G0480, 80306, G0482, 0603U, 80305.
What ICD-9 codes does G40.309 map to? +
Per CMS GEMs, G40.309 maps to ICD-9 codes: 34510. 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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