F18.99 ICD-10-CM Code: Inhalant use, unspecified with unspecified inhalant-induced disorder
HCC Buddy Code Card
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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)
F18.99
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceInhalant use, unspecified with unspecified inhalant-induced disorder
A person with unspecified inhalant use who has an unspecified disorder caused by inhalant exposure, when the exact nature of the disorder is not documented.
Buddy Insight
This code captures an unspecified substance-induced disorder from inhalant use, where the specific nature of the complication is not documented.
CMS-HCC V28
MappedHCC 137
RAF 0.424
CMS-HCC V24
MappedHCC 55
RAF 0.329
ACA/HHS
MappedHCC 82
Varies by metal level
ESRD/PACE
MappedHCC 55
RAF 0.111
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for F18.99 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for F18.99 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for F18.99 in this effective period.
Excludes 1
Official- inhalant abuse (F18.1-)
- inhalant dependence (F18.2-)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for F18.99 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for F18.99 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for F18.99 in this effective period.
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 F18.99 an HCC code?
Yes. F18.99 (Inhalant use, unspecified with unspecified inhalant-induced disorder) maps to Drug Use Disorder, Moderate/Severe, or Drug Use with Non-Psychotic Complications under the CMS-HCC V28 risk adjustment model (and Substance Use Disorder, Moderate/Severe, or Substance Use with Complications under V24), with a community non-dual aged RAF of 0.424. It is billable for payment year 2026.
Coder answer: F18.99 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
- F18.99
- Description
- Inhalant use, unspecified with unspecified inhalant-induced disorder
- HCC (V28)
- HCC 137 — Drug Use Disorder, Moderate/Severe, or Drug Use with Non-Psychotic Complications
- RAF
- 0.424
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
Each model's RAF is its CMS base weight for that model's standard population, so 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 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.
Work F18.99 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for F18.99
For F18.99 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 F18.99 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
F18.99 is the ICD-10-CM diagnosis code for inhalant use, unspecified with unspecified inhalant-induced disorder. A person with unspecified inhalant use who has an unspecified disorder caused by inhalant exposure, when the exact nature of the disorder is not documented. F18.99 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, F18.99 maps to Drug Use Disorder, Moderate/Severe, or Drug Use with Non-Psychotic Complications (HCC 137) with a community, non-dual, aged base RAF weight of 0.424. Under the older CMS-HCC V24 model, F18.99 maps to Substance Use Disorder, Moderate/Severe, or Substance Use with Complications (HCC 55) with a community, non-dual, aged base RAF weight of 0.329. 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 less specific code; attempt to identify the specific inhalant-induced disorder when possible. Because F18.99 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 F18.99 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a less specific code; attempt to identify the specific inhalant-induced disorder when possible
- •Use only when documentation does not support a more specific diagnosis code
Clinical Significance
This code captures an unspecified substance-induced disorder from inhalant use, where the specific nature of the complication is not documented. While less specific codes should be avoided when possible, this code still reflects that the substance use is causing identifiable clinical complications. Querying for additional specificity is recommended to support optimal risk adjustment.
Documentation Requirements
- ✓Provider documentation of inhalant use, specifying the type of inhalant when known (e.g., toluene, gasoline, aerosol propellants, nitrites)
- ✓Documentation of substance use pattern; query provider to determine if abuse or dependence criteria are met for more specific coding
- ✓Assessment and plan addressing the substance use disorder with treatment approach documented
Commonly Confused Codes
- •F18.10-F18.19 (Inhalant abuse codes): use when documentation supports a pattern of harmful use without dependence
- •F18.20-F18.29 (Inhalant dependence codes): use when documentation supports physiological or psychological dependence
- •F19.x codes (Other psychoactive substance use): F19 is for substances other than inhalants; use F18 specifically when the substance is an inhalant