2027 ICD-10-CM Diagnosis Code F40.228Other natural environment type phobia

ICD-10-CM Codes›F01–F99›F40-F48›F40

ICD-10-CM F40.228
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

F40.228 is a billable ICD-10-CM diagnosis code for other natural environment type phobia. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 882. Coders also document this condition as fear of natural phenomena. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Anxiety and fear-related disorders.

F40.228 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model. It still risk-adjusts in the RxHCC Part D (V08) category 133 for payment year 2027.

Code Identity

ICD-10-CM Code
F40.228
Billable Status
Yes — Valid for Submission
Code Describes
Other natural environment type phobia
Short Description
Other natural environment type phobia
Same as the full description in the CMS dataset.
Parent Code
F40.22
Natural environment type phobia

Code Classification

ChapterF01–F99Mental and behavioural disorders
SectionF40-F48Anxiety, dissociative, stress-related, somatoform and other nonpsychotic mental disorders
CategoryF40Phobic anxiety disorders
This CodeF40.228Other natural environment type phobia

Medicare Risk Adjustment (HCC)Billing

F40.228 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model, but it maps to payment categories in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
no payment category in the model that pays 100% of MA risk scores
Prior Model (CMS-HCC V24)
Not mapped under V24
this diagnosis newly risk-adjusts under the V28 model
Part D (RxHCC)
RxHCC 133 — Anxiety and Other Psychiatric Disorders
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Fear of natural phenomena
  • Fear of water

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to F40.228: its own notes plus those printed at F40.2 and Chapter 5. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Chapter 5 (F01-F99) Mental and behavioural disorders applies to 872 codes
  • disorders of psychological development

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From F40.2 Specific (isolated) phobias applies to 16 codes
From Chapter 5 (F01-F99) Mental and behavioural disorders applies to 872 codes
  • symptoms, signs and abnormal clinical laboratory findings, not elsewhere classified (R00-R99)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name F40.228, its category, or a range that includes it.

Excludes2 3

These codes carry an Excludes2 note naming F40.228: its condition is not part of those codes, and both may be reported when the patient has both.

  • F06.4 Anxiety disorder due to known physiological condition
    anxiety disorders, not due to known physiological condition or unspecified (F40.-, F41.-) names F40.-, which includes this code
  • F90 Attention-deficit hyperactivity disorders
    anxiety disorders (F40.-, F41.-) names F40.-, which includes this code
  • F93.0 Separation anxiety disorder of childhood
    nonpsychotic mental disorders (F40-F48) names F40-F48, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR MBD005
Anxiety and fear-related disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Phobias

A phobia is a type of anxiety disorder. It is a strong, irrational fear of something that poses little or no real danger.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert F40.228 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
300.29 Isolated/spec phobia NEC
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About F40.228Overview

What is the ICD-10 code for other natural environment type phobia?

The ICD-10-CM code for other natural environment type phobia is F40.228 (sometimes written as F40228). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is F40.228 (Natural environment type phobia) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other natural environment type phobia on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does F40.228 group to?

When other natural environment type phobia is the principal diagnosis on an inpatient stay, it groups to MS-DRG 882 (neuroses Except Depressive), which carries a relative weight of 0.9953. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of F40.228?

Under the General Equivalence Mappings, other natural environment type phobia converts to ICD-9-CM 300.29 (isolated/spec phobia NEC). The mapping is approximate, so confirm the match fits the documentation.

Does F40.228 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage: F40.228 maps to no category in the CMS-HCC V28 model. It still risk-adjusts in the RxHCC Part D (V08) category 133 (Anxiety and Other Psychiatric Disorders).