ICD-10 Code G40.3 – Generalized idiopathic epilepsy and epileptic syndromes (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G40.3 – Generalized idiopathic epilepsy and epileptic syndromes
What it is
G40.3 identifies generalized idiopathic epilepsy and related epileptic syndromes. Use it for epilepsy that begins with generalized seizure activity and is not explained by a known structural, metabolic, or infectious cause.
Clinical signs
Clinical features vary; refer to documentation. Typical notes include generalized seizure types, such as absence, myoclonic, or generalized tonic-clonic events, with normal or near-normal neurologic examination between episodes.
When to use this code
Use this code when the provider documents generalized idiopathic epilepsy or a matching generalized epileptic syndrome. It is appropriate when the record supports a primary generalized epilepsy diagnosis and does not identify a secondary cause. Check documentation if the seizure type or syndrome is unspecified.
Do not use for
Do not use this code for focal epilepsy, symptomatic epilepsy, or seizures due to another condition. If the documentation only states “seizure” without an epilepsy diagnosis, code the documented symptom instead.
Coding tip
Confirm the provider’s exact epilepsy type and syndrome wording before assigning G40.3.