G61.1
BillableSerum neuropathy
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G61.1 an HCC code?
Yes. G61.1 maps to Myasthenia Gravis/Myoneural Conditions and Guillain-Barre Syndrome under the V24 model but is not retained in V28.
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 G61.1
For G61.1to 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 G61.1 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G61.1 is the ICD-10-CM diagnosis code for serum neuropathy. Nerve damage that develops as a reaction to a serum injection or vaccine, causing inflammation and weakness in multiple nerves. G61.1 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering polyneuropathies and other disorders of the peripheral nervous system (g60-g65).
Under the older CMS-HCC V24 model, G61.1 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 serum or vaccine that triggered the reaction when possible. Because G61.1 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 G61.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document the specific serum or vaccine that triggered the reaction when possible
- •Link this diagnosis to the administration of the causative serum or vaccine for complete clinical picture
Clinical Significance
Serum neuropathy is an immune-mediated nerve damage triggered by serum or vaccine administration, representing an adverse reaction that requires ongoing monitoring and treatment. Capturing this diagnosis is important for risk adjustment as it reflects a patient with complex neurological needs and potential long-term disability. It also has implications for adverse event tracking and pharmacovigilance.
Documentation Requirements
- ✓Identification of the specific serum or vaccine that triggered the neuropathy
- ✓Temporal relationship between serum/vaccine administration and symptom onset
- ✓Clinical findings: weakness, numbness, nerve conduction study results
- ✓Distinction from other inflammatory polyneuropathies
- ✓Provider's explicit statement linking the neuropathy to serum/vaccine exposure
- ✓Current treatment and management plan
Use Additional Code
- code for adverse effect, if applicable, to identify serum (T50.-)
Commonly Confused Codes
- •G61.0 — Guillain-Barre syndrome is an autoimmune polyneuropathy not specifically triggered by serum; use G61.1 when causally linked to serum/vaccine
- •G61.89 — Other inflammatory polyneuropathies should be used only when the specific cause is not serum-related
- •T50.Z95A — Adverse effect of vaccines initial encounter captures the adverse event itself, not the resulting neuropathy
- •G62.0 — Drug-induced polyneuropathy is for medication-caused neuropathy, not serum/vaccine-triggered