F40.228 ICD-10-CM Code: Other natural environment type phobia
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FY 2026 Apr update / Mental, Behavioral and Neurodevelopmental disorders (F01-F99) / Anxiety, dissociative, stress-related, somatoform and other nonpsychotic mental disorders (F40-F48)
F40.228
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOther natural environment type phobia
An intense, irrational fear of natural environmental phenomena other than thunderstorms, such as heights, water, or darkness.
Buddy Insight
Other natural environment type phobia covers specific phobias related to natural environment stimuli other than thunderstorms (which has its own code), such as fear of water, darkness, or natural disasters.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
N/A—
Not mapped
ACA/HHS
N/A—
Not mapped
ESRD/PACE
N/A—
Not mapped
RXHCC
MappedHCC 133
RAF 0.035
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for F40.228 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for F40.228 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for F40.228 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for F40.228 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for F40.228 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for F40.228 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for F40.228 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 F40.228 an HCC code?
F40.228 is not in the CMS-HCC V28 or V24 community payment model, but it does map to Personality Disorders, Anxiety, and Other Specified Mental Disorders under the Part D RxHCC model.
- Code
- F40.228
- Description
- Other natural environment type phobia
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF
- —
- 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 F40.228 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for F40.228
For F40.228 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 F40.228 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
F40.228 is the ICD-10-CM diagnosis code for other natural environment type phobia. An intense, irrational fear of natural environmental phenomena other than thunderstorms, such as heights, water, or darkness. F40.228 sits in the ICD-10-CM chapter for mental, behavioral and neurodevelopmental disorders (f01-f99), within the section covering anxiety, dissociative, stress-related, somatoform and other nonpsychotic mental disorders (f40-f48).
F40.228 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
This code does not map to a CMS-HCC V28 payment category. Capture depends on documentation that supports the diagnosis; verify the HCC assignment against the current CMS mapping for the applicable payment year. Coders reviewing F40.228 should check whether additional documentation would support a more specific child code in the same hierarchy that does map to a payment HCC, capturing the correct specificity is the highest-impact RAF improvement available within accurate coding.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for F40.228 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code for natural environment phobias not specifically coded elsewhere
- •Specify the environmental trigger in documentation (heights, water, wind, etc.)
Clinical Significance
Other natural environment type phobia covers specific phobias related to natural environment stimuli other than thunderstorms (which has its own code), such as fear of water, darkness, or natural disasters. These phobias can significantly affect quality of life depending on geographic and lifestyle factors. It is not risk-adjusting under any HCC model.
Documentation Requirements
- ✓Specific natural environment stimulus feared (water, darkness, earthquakes, etc.)
- ✓Marked fear disproportionate to actual danger
- ✓Consistent anxiety response upon exposure or anticipation
- ✓Active avoidance or endurance with intense distress
- ✓Duration of 6+ months
- ✓Functional impairment documented
Commonly Confused Codes
- •F40.220 (Fear of thunderstorms): Use the specific code F40.220 for thunderstorm phobia rather than the residual category
- •F40.241 (Acrophobia): Fear of heights has its own specific code and should not be coded under F40.228
- •F40.218 (Other animal type phobia): Distinguish between fear of animals versus fear of natural environments