G70.1
BillableToxic myoneural disorders
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G70.1 an HCC code?
Yes. G70.1 maps to Myasthenia Gravis/Myoneural Conditions and Guillain-Barre under the CMS-HCC V28 risk adjustment model (and Myasthenia Gravis/Myoneural Conditions and Guillain-Barre Syndrome 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 G70.1
For G70.1 to 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 G70.1 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G70.1 is the ICD-10-CM diagnosis code for toxic myoneural disorders. Muscle weakness and dysfunction caused by exposure to toxic substances that damage the connection between nerves and muscles. G70.1 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering diseases of myoneural junction and muscle (g70-g73).
Under the CMS-HCC V28 risk adjustment model, G70.1 maps to Myasthenia Gravis/Myoneural Conditions and Guillain-Barre (HCC 196) with a community, non-dual, aged base RAF weight of 0.402. Under the older CMS-HCC V24 model, G70.1 maps to Myasthenia Gravis/Myoneural Conditions and Guillain-Barre Syndrome (HCC 75) with a community, non-dual, aged base RAF weight of 0.425. 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.
Document the specific toxic agent when possible (e.g., organophosphates, heavy metals, medications). Because G70.1 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 G70.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document the specific toxic agent when possible (e.g., organophosphates, heavy metals, medications)
- •Verify that the myoneural disorder is directly related to toxin exposure rather than another etiology
Clinical Significance
Toxic myoneural disorders represent damage to the neuromuscular junction caused by toxic substances such as organophosphates, botulinum toxin, or certain medications. These conditions can be acutely life-threatening due to respiratory muscle paralysis. Accurate coding captures the severity of the toxic exposure and the specialized care required for neuromuscular recovery.
Documentation Requirements
- ✓Identification of the specific toxic agent causing the myoneural disorder
- ✓Clinical evidence of neuromuscular junction dysfunction: weakness, fatigability, respiratory compromise
- ✓Electrodiagnostic studies showing neuromuscular transmission defect when available
- ✓Temporal relationship between toxic exposure and symptom onset
- ✓Treatment administered: antidotes, supportive care, respiratory support
- ✓Provider's explicit diagnosis linking the myoneural disorder to toxic exposure