ICD-10 F16.121
Billable / Specific HCC v28: 55 CCHallucinogen abuse with intoxication with delirium
About ICD-10-CM F16.121
ICD-10-CM code F16.121 represents Hallucinogen abuse with intoxication with delirium. This is a billable/specific code in the Mental, Behavioral, and Neurodevelopmental chapter (block F16). The 2026 edition of ICD-10-CM F16.121 became effective on October 1, 2025.
Coding Tips for F16.121
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
F16.121 is a CMS-HCC v28 risk-adjustment code (category 55). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
F16.121 is designated CC for MS-DRG grouping. On inpatient claims, this code can shift the DRG to the with-CC variant when documented as a present-on-admission secondary diagnosis. Hospital CDI programs flag CC opportunities during chart review. Failure to capture this code may leave 30 to 80 percent of the inpatient stay revenue unrealized.
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Inpatient DRG Impact, CC
codes Hallucinogen abuse with intoxication with delirium. As a Complication/Comorbidity (CC), this contributes to DRG severity adjustment when documented alongside the principal diagnosis.
Medicare LCD Coverage for F16.121
Local Coverage Determinations (LCDs) from CMS MACs that list F16.121 as a covered diagnosis.
Showing top 10 of 300 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing F16.121.
1 Cigna
5 Medicare
CPT Codes Commonly Billed with F16.121
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
We don't have CPT pairings indexed for this specific code yet. Use the CPT search above to find common procedures, or check your payer's published medical policy for code-specific guidance.
Convert F16.121 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| F16.121 | 29281 | 10000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To F16.121
Other codes in section F10-F19 (Mental and behavioral disorders due to psychoactive substance use).
ICD-10 F16.121, Billing FAQ
Is ICD-10 code F16.121 billable? +
Yes, F16.121 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
Does F16.121 affect Medicare Advantage HCC risk adjustment? +
Yes. F16.121 maps to CMS-HCC v28 category 55. Capture this diagnosis annually for accurate Medicare Advantage risk score.
Is F16.121 a CC or MCC for inpatient DRG? +
Yes, this code is designated as CC. Documenting as a secondary diagnosis on inpatient claims can shift the DRG to a higher-weighted category.
What ICD-9 codes does F16.121 map to? +
Per CMS GEMs, F16.121 maps to ICD-9 codes: 29281. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on May 31, 2026.
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