G40.009
BillableLocalization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, not intractable, without status epilepticus
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G40.009 an HCC code?
Yes. G40.009 maps to Seizure Disorders and Convulsions under the CMS-HCC V28 risk adjustment model (and Seizure Disorders and Convulsions under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for G40.009
For G40.009to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed G40.009 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G40.009 is the ICD-10-CM diagnosis code for localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, not intractable, without status epilepticus. This is a type of epilepsy that starts in a specific area of the brain and causes seizures that remain localized to that region. The seizures can be controlled with medication and the patient is not currently experiencing status epilepticus (prolonged or repeated seizures without recovery). G40.009 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering episodic and paroxysmal disorders (g40-g47).
Under the CMS-HCC V28 risk adjustment model, G40.009 maps to Seizure Disorders and Convulsions (HCC 201) with a community, non-dual, aged base RAF weight of 0.262. Under the older V24 model, G40.009 mapped to the same category but with a base RAF weight of 0.244 — V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Verify that the epilepsy is confirmed as idiopathic (no identifiable cause) and localization-related before assigning this code, as other epilepsy types have different code families. Because G40.009 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for G40.009 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify that the epilepsy is confirmed as idiopathic (no identifiable cause) and localization-related before assigning this code, as other epilepsy types have different code families
- •Ensure documentation confirms the seizures are NOT intractable (not drug-resistant) and the patient is NOT in status epilepticus, as these conditions require different 7th character codes (the '9' indicates these conditions are absent)
Clinical Significance
This code represents the most common presentation of focal idiopathic epilepsy — well-controlled with medication and not in status epilepticus. It is the baseline code for patients with localization-related epilepsy of unknown cause who are doing well on their current treatment regimen. Accurate annual capture ensures proper risk adjustment for ongoing epilepsy management.
Documentation Requirements
- ✓Documentation confirming localization-related (focal) epilepsy diagnosis
- ✓Documentation that the epilepsy is idiopathic (no identified cause)
- ✓Current medication regimen and seizure control status
- ✓Statement that seizures are not intractable (controlled with medication)
- ✓Confirmation that patient is NOT in status epilepticus
- ✓Last seizure date and seizure frequency if documented
Commonly Confused Codes
- •G40.001 — Same epilepsy type with status epilepticus; use during acute status epilepticus event
- •G40.019 — Same epilepsy type, intractable, without status epilepticus; for drug-resistant cases
- •G40.109 — Symptomatic focal epilepsy with simple partial seizures; has an identified cause
- •G40.209 — Symptomatic focal epilepsy with complex partial seizures; has impaired awareness
- •G40.909 — Epilepsy, unspecified, not intractable; too nonspecific when focal type is documented