F16.121 ICD-10-CM Code: Hallucinogen abuse with intoxication with delirium
F16.121 maps to CMS-HCC V28 137. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software
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FY 2026 Apr update / Mental, Behavioral and Neurodevelopmental disorders (F01-F99) / Mental and behavioral disorders due to psychoactive substance use (F10-F19)
F16.121
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceHallucinogen abuse with intoxication with delirium
Misuse of hallucinogenic drugs (like LSD or psilocybin) with acute confusion and disorientation during intoxication.
Buddy Insight
Hallucinogen abuse with intoxication delirium is a medical emergency where hallucinogenic drug use produces acute delirium with disorientation, confusion, and potential for dangerous behavior.
CMS-HCC V28
MappedHCC 137
Coefficient HCC 137: 0.424 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 082
Code-level coefficient reference
ESRD/PACE
MappedHCC 55
Code-level coefficient reference
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for F16.121. Check the code and parent instructions in the Code Book.
Excludes 2
Official- symptoms, signs and abnormal clinical laboratory findings, not elsewhere classified (R00-R99)Inherited from F01-F99
Related Codes
Includes
Official- disorders of psychological developmentInherited from F01-F99, F16
- ecstasyInherited from F01-F99, F16
- PCPInherited from F01-F99, F16
- phencyclidineInherited from F01-F99, F16
Excludes 1
Official- hallucinogen dependence (F16.2-)Inherited from F16.1
- hallucinogen use, unspecified (F16.9-)Inherited from F16.1
Code First
OfficialNo Code First sequencing instructions are included in this display for F16.121. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for F16.121. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for F16.121. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is F16.121 an HCC code?
Yes. F16.121 (Hallucinogen abuse with intoxication with delirium) maps to HCC 137, Drug Use Disorder, Moderate/Severe, or Drug Use with Non-Psychotic Complications under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.424. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: F16.121 is billable and maps to V28 HCC 137, Drug Use Disorder, Moderate/Severe, or Drug Use with Non-Psychotic Complications. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- F16.121
- Description
- Hallucinogen abuse with intoxication with delirium
- HCC (V28)
- HCC 137 — Drug Use Disorder, Moderate/Severe, or Drug Use with Non-Psychotic Complications
- RAF reference coefficient
- 0.424
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work F16.121 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for F16.121
For F16.121, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
Coder workflow notes
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What This Code Means
F16.121 is the ICD-10-CM diagnosis code for hallucinogen abuse with intoxication with delirium. Misuse of hallucinogenic drugs (like LSD or psilocybin) with acute confusion and disorientation during intoxication. F16.121 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, F16.121 maps to Drug Use Disorder, Moderate/Severe, or Drug Use with Non-Psychotic Complications (HCC 137) with a source-labeled community, non-dual, aged reference coefficient of 0.424. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
This code requires documentation of both hallucinogen abuse and delirium as a specific manifestation of intoxication. For F16.121, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for F16.121 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code requires documentation of both hallucinogen abuse and delirium as a specific manifestation of intoxication
- •Delirium must be present during the acute intoxication period, not as a separate condition
Clinical Significance
Hallucinogen abuse with intoxication delirium is a medical emergency where hallucinogenic drug use produces acute delirium with disorientation, confusion, and potential for dangerous behavior. This is more common with PCP-type hallucinogens but can occur with any hallucinogenic substance at high doses. Patients may require physical restraint, sedation, and intensive monitoring for safety.
Documentation Requirements
- ✓Documented hallucinogen abuse
- ✓Clinical evidence of acute intoxication from hallucinogens
- ✓Delirium criteria documented: acute onset confusion, altered consciousness, disorientation, fluctuating mental status
- ✓Specific hallucinogen identified when possible
- ✓Safety interventions, level of monitoring, and any restraint use documented
Commonly Confused Codes
- •F16.120: Hallucinogen abuse with uncomplicated intoxication; no delirium present
- •F16.122: Hallucinogen abuse with intoxication with perceptual disturbance; perceptual changes without full delirium
- •F05: Delirium due to known physiological condition; non-substance-related delirium
- •F16.221: Hallucinogen dependence with intoxication delirium; requires documented dependence