F31.9
BillableBipolar disorder, unspecified
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is F31.9 an HCC code?
Yes. F31.9 maps to Bipolar Disorders under the CMS-HCC V28 risk adjustment model (and Major Depressive, Bipolar, and Paranoid Disorders 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 F31.9
For F31.9 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 F31.9 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
F31.9 is the ICD-10-CM diagnosis code for bipolar disorder, unspecified. Bipolar disorder diagnosed but without enough information to specify the type, severity, or current episode status. F31.9 sits in the ICD-10-CM chapter for mental, behavioral and neurodevelopmental disorders (f01-f99), within the section covering mood [affective] disorders (f30-f39).
Under the CMS-HCC V28 risk adjustment model, F31.9 maps to Bipolar Disorders (HCC 154) with a community, non-dual, aged base RAF weight of 0.265. Under the older CMS-HCC V24 model, F31.9 maps to Major Depressive, Bipolar, and Paranoid Disorders (HCC 59) with a community, non-dual, aged base RAF weight of 0.309. 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 is a non-specific code; use only when more specific bipolar codes cannot be determined from documentation. Because F31.9 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 F31.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a non-specific code; use only when more specific bipolar codes cannot be determined from documentation
- •Query the provider for additional details to assign a more specific bipolar code
Clinical Significance
Bipolar disorder, unspecified is used when the provider documents a bipolar diagnosis but does not specify the type (I vs II), current episode (manic, depressed, mixed), or remission status. While this code captures the diagnosis for risk adjustment, it represents a documentation improvement opportunity. Querying for specificity improves both clinical care and coding accuracy.
Documentation Requirements
- ✓Provider documentation of bipolar disorder as a diagnosis
- ✓Current symptom status or episode type should be queried if not documented
- ✓Treatment plan consistent with bipolar disorder management
- ✓Medication list supporting the diagnosis (mood stabilizers, atypical antipsychotics)
- ✓Provider should be queried for: current episode type, severity, remission status, type I vs II
Commonly Confused Codes
- •F31.81 — Bipolar II disorder: Specific type that should be coded when documented
- •F31.0-F31.64 — Episode-specific bipolar codes: Use when current episode type and severity are documented
- •F39 — Unspecified mood disorder: Use when bipolar is not confirmed, only mood disorder
- •F31.70 — Bipolar disorder, remission: Use when remission is documented even if episode type is unspecified