R40.20
BillableUnspecified coma
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is R40.20 an HCC code?
Yes. R40.20 maps to Coma, Brain Compression/Anoxic Damage under the CMS-HCC V28 risk adjustment model (and Coma, Brain Compression/Anoxic Damage 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 R40.20
For R40.20 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 R40.20 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
R40.20 is the ICD-10-CM diagnosis code for unspecified coma. A state of complete unconsciousness where the patient cannot be awakened and the cause is not specified. R40.20 sits in the ICD-10-CM chapter for symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (r00-r99), within the section covering symptoms and signs involving cognition, perception, emotional state and behavior (r40-r46).
Under the CMS-HCC V28 risk adjustment model, R40.20 maps to Coma, Brain Compression/Anoxic Damage (HCC 202) with a community, non-dual, aged base RAF weight of 0.000. Under the older V24 model, R40.20 mapped to the same category but with a base RAF weight of 0.546 — 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.
This code should only be used when the coma is unspecified; if the cause is known, use a more specific coma code. Because R40.20 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 R40.20 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code should only be used when the coma is unspecified; if the cause is known, use a more specific coma code
- •Always attempt to determine if the coma is traumatic or nontraumatic, as this affects code selection
Clinical Significance
Unspecified coma represents a state of profound unconsciousness where the patient cannot be aroused and shows no purposeful responses. This condition carries significant mortality risk and requires intensive monitoring, supportive care, and investigation into the underlying cause while representing substantial resource utilization.
Documentation Requirements
- ✓Documentation of unresponsive state
- ✓Glasgow Coma Scale score if assessed
- ✓Duration of coma
- ✓Level of consciousness assessment
- ✓Neurological examination findings
- ✓Investigations performed to determine cause
- ✓Response to stimuli documented
- ✓Associated complications or supportive measures