What is ICD-10 code G43.401?

G43.401 is the ICD-10-CM diagnosis code for Hemiplegic migraine, not intractable, with status migrainosus. A rare type of migraine causing temporary weakness on one side of the body that responds to treatment but is currently in a prolonged migraine state. G43.401 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. G43.401 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. G43.401 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. G43.401 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for G43.401?

G43.401 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards G43.401 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

What should coders know when reporting G43.401?

Hemiplegic migraine can mimic stroke; ensure neurological examination findings are documented Status migrainosus with hemiplegic migraine requires careful monitoring for complications

G43.401: Hemiplegic migraine, not intractable, with status migrainosus — ICD-10

ICD-10-CM Code View

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Code lookupG43.401Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Episodic and paroxysmal disorders (G40-G47)

G43.401

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Hemiplegic migraine, not intractable, with status migrainosus

A rare type of migraine causing temporary weakness on one side of the body that responds to treatment but is currently in a prolonged migraine state.

Buddy Insight

Hemiplegic migraine is a rare and serious migraine subtype characterized by temporary motor weakness or paralysis on one side of the body, mimicking stroke presentation.

CMS-HCC V28

Not risk-adjusted for this model/period.

RAF 0

CMS-HCC V24

Not risk-adjusted for this model/period.

RAF 0

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Not risk-adjusted for this model/period.

RAF 0

RXHCC

Mapped

HCC 166

Migraine

RAF 0.0

Code Trumping

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Code Book Path

Official

G43.4Hemiplegic migraine

G43.40Hemiplegic migraine, not intractable

G43.401Hemiplegic migraine, not intractable, with status migrainosus

Inclusion Terms

Official

Hemiplegic migraine without refractory migraine

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for G43.401 in this effective period.

Related Child Codes

Official

G43.409Hemiplegic migraine, not intractable, without status migrainosus

Includes

Official

ICD-10-CM does not list Includes notes for G43.401 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for G43.401 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for G43.401 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for G43.401 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for G43.401 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documented unilateral motor weakness or hemiplegia during migraine episode

Neurological examination findings differentiating from stroke (reversibility, associated aura symptoms)

Characterization as not intractable (responsive to treatment) vs. intractable

Status migrainosus documentation: migraine lasting >72 hours with notation of duration

MEAT Support

HCC Buddy guidance

Documented unilateral motor weakness or hemiplegia during migraine episode

Neurological examination findings differentiating from stroke (reversibility, associated aura symptoms)

Characterization as not intractable (responsive to treatment) vs. intractable

Status migrainosus documentation: migraine lasting >72 hours with notation of duration

Audit Caution

HCC Buddy guidance

Failing to distinguish hemiplegic migraine from common migraine with aura — motor weakness is the defining feature

Not clarifying intractable vs. not intractable status; intractable means the migraine has failed to respond to treatment

Confusing status migrainosus (>72 hours) with a severe but shorter episode; duration must be documented

Coding stroke (I63.x) when presentation is actually hemiplegic migraine — always verify with imaging

Common Mistakes

HCC Buddy guidance

G43.001-G43.019 (Migraine without aura) — lacks the motor weakness/hemiplegia component that defines hemiplegic migraine

G43.101-G43.119 (Migraine with aura) — has sensory/visual aura but NOT motor weakness; hemiplegic migraine specifically requires motor involvement

I63.x (Cerebral infarction) — hemiplegic migraine mimics stroke but is reversible; requires imaging to differentiate

G43.601-G43.619 (Persistent migraine aura with cerebral infarction) — use when migraine aura symptoms persist AND imaging confirms infarction

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is G43.401 an HCC code?

No. G43.401 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.

HCC Category Mapping

RxHCCHCC 166, Migraine

0.000

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.

Work G43.401 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for G43.401

For G43.401to 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 G43.401 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

G43.401 is the ICD-10-CM diagnosis code for hemiplegic migraine, not intractable, with status migrainosus. A rare type of migraine causing temporary weakness on one side of the body that responds to treatment but is currently in a prolonged migraine state. G43.401 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).

G43.401 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.

Maps to RxHCC 166 (Severe Head Injury) with a RAF weight of 0.000 in the prescription drug model. This code does NOT map to any CMS-HCC under V28 or V24 payment models, so it does not directly affect Medicare Advantage RAF scores. The RxHCC mapping primarily influences pharmacy cost predictions. No hierarchies apply within the CMS-HCC payment models for this code.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for G43.401 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Hemiplegic migraine can mimic stroke; ensure neurological examination findings are documented
•Status migrainosus with hemiplegic migraine requires careful monitoring for complications

Clinical Significance

Hemiplegic migraine is a rare and serious migraine subtype characterized by temporary motor weakness or paralysis on one side of the body, mimicking stroke presentation. Accurate coding is critical because hemiplegic migraine requires distinct management protocols and may indicate increased cerebrovascular risk. This code maps to RxHCC 166 (Severe Head Injury) in the prescription drug risk adjustment model, impacting pharmacy cost predictions.

Documentation Requirements

✓Documented unilateral motor weakness or hemiplegia during migraine episode
✓Neurological examination findings differentiating from stroke (reversibility, associated aura symptoms)
✓Characterization as not intractable (responsive to treatment) vs. intractable
✓Status migrainosus documentation: migraine lasting >72 hours with notation of duration
✓Family history of hemiplegic migraine if applicable (familial vs. sporadic subtype)
✓Neuroimaging results (CT/MRI) to exclude cerebrovascular accident
✓Current treatment plan and medication regimen

Commonly Confused Codes

•G43.001-G43.019 (Migraine without aura): lacks the motor weakness/hemiplegia component that defines hemiplegic migraine
•G43.101-G43.119 (Migraine with aura): has sensory/visual aura but NOT motor weakness; hemiplegic migraine specifically requires motor involvement
•I63.x (Cerebral infarction): hemiplegic migraine mimics stroke but is reversible; requires imaging to differentiate
•G43.601-G43.619 (Persistent migraine aura with cerebral infarction): use when migraine aura symptoms persist AND imaging confirms infarction
•G81.x (Hemiplegia/hemiparesis): sequela codes for established paralysis, not episodic migraine-related weakness

Child Codes

G43.401Hemiplegic migraine, not intractable, with status migrainosus

G43.409Hemiplegic migraine, not intractable, without status migrainosus

Code Hierarchy

└G43Migraine └G43.4Hemiplegic migraine └G43.40Hemiplegic migraine, not intractable └G43.401Hemiplegic migraine, not intractable, with status migrainosus

└G43.401Hemiplegic migraine, not intractable, with status migrainosus

G43.401 ICD-10-CM Code: Hemiplegic migraine, not intractable, with status migrainosus

HCC Buddy Code Card

G43.401

Is G43.401 an HCC code?

HCC Category Mapping

MEAT Criteria for G43.401

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What This Code Means

Coding Tips

Clinical Significance

Documentation Requirements

Commonly Confused Codes

Child Codes

Code Hierarchy

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