F16.99
BillableHallucinogen use, unspecified with unspecified hallucinogen-induced disorder
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is F16.99 an HCC code?
Yes. F16.99 maps to Drug Use Disorder/Substance Use Disorder, Moderate/Severe under the CMS-HCC V28 risk adjustment model (and Drug/Alcohol Dependence 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 F16.99
For F16.99 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 F16.99 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
F16.99 is the ICD-10-CM diagnosis code for hallucinogen use, unspecified with unspecified hallucinogen-induced disorder. A condition involving unspecified hallucinogenic drug use with unspecified health problems caused by the drug, where neither the specific hallucinogen nor the specific disorder is clearly identified. F16.99 sits in the ICD-10-CM chapter for mental, behavioral and neurodevelopmental disorders (f01-f99), within the section covering mental and behavioral disorders due to psychoactive substance use (f10-f19).
Under the CMS-HCC V28 risk adjustment model, F16.99 maps to Drug Use Disorder/Substance Use Disorder, Moderate/Severe (HCC 137) with a community, non-dual, aged base RAF weight of 0.358. Under the older CMS-HCC V24 model, F16.99 maps to Drug/Alcohol Dependence (HCC 55) with a community, non-dual, aged base RAF weight of 0.334. 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 the least specific hallucinogen use code; use only when documentation lacks detail about both the substance and induced disorder. Because F16.99 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 F16.99 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is the least specific hallucinogen use code; use only when documentation lacks detail about both the substance and induced disorder
- •Query the provider if more specific information about the hallucinogen type or induced disorder can be documented
Clinical Significance
This is the least specific hallucinogen use code — unspecified use pattern with unspecified induced disorder. It indicates significant documentation gaps in both the substance use pattern and the nature of complications. While it still captures HCC value, it represents the lowest quality coding in this category.
Documentation Requirements
- ✓Minimum documentation of hallucinogen use with some induced disorder
- ✓Provider queries for both the use pattern and specific disorder type
- ✓Clinical justification for why specificity cannot be achieved
- ✓Follow-up plan for comprehensive substance use evaluation
- ✓Any available clinical signs or symptoms documented
Commonly Confused Codes
- •F16.90 — Hallucinogen use, unspecified, uncomplicated; use when NO induced disorder exists
- •F16.988 — With other specified induced disorder; preferred when the disorder IS identified
- •F16.959 — With psychotic disorder; if psychosis exists, this code captures higher HCC value
- •F16.29 — Hallucinogen dependence with unspecified disorder; more specific regarding dependence