What is ICD-10 code F45.21?

F45.21 is the ICD-10-CM diagnosis code for Hypochondriasis. An excessive and persistent worry about having a serious disease or illness, often accompanied by frequent health-related behaviors like checking for symptoms or seeking reassurance. It belongs to the ICD-10-CM chapter for mental, behavioral and neurodevelopmental disorders (f01-f99). F45.21 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. F45.21 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. F45.21 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. F45.21 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for F45.21?

F45.21 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither community model rewards F45.21 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's V28/V24 community RAF score in either version. It does, however, map under the Part D RxHCC model (Personality Disorders, Anxiety, and Other Specified Mental Disorders), which affects the ESRD and/or Part D (RxHCC) risk scores. Coders should check whether provider documentation supports a more specific child code that does map to a community payment HCC.

What should coders know when reporting F45.21?

Distinguish from health anxiety by documenting the preoccupation with having disease rather than fear of getting it Note that reassurance-seeking and body checking behaviors are common features

F45.21: Hypochondriasis — ICD-10

ICD-10-CM Code View

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Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupF45.21Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Mental, Behavioral and Neurodevelopmental disorders (F01-F99) / Anxiety, dissociative, stress-related, somatoform and other nonpsychotic mental disorders (F40-F48)

F45.21

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Hypochondriasis

An excessive and persistent worry about having a serious disease or illness, often accompanied by frequent health-related behaviors like checking for symptoms or seeking reassurance.

Buddy Insight

Hypochondriasis is the specific form of illness anxiety disorder characterized by persistent conviction of having a serious, undiagnosed disease despite repeated negative medical evaluations.

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ACA/HHS

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ESRD/PACE

N/A

—

Not risk-adjusted for this model/period.

Not mapped

RXHCC

Mapped

HCC 133

Personality Disorders, Anxiet...

RAF 0.035

Code Book Path

Official

F45Somatoform disorders

F45.2Hypochondriacal disorders

F45.21Hypochondriasis

Inclusion Terms

Official

Hypochondriacal neurosis
Illness anxiety disorder

Excludes 2

Official

delusional dysmorphophobia (F22)
fixed delusions about bodily functions or shape (F22)

Related Child Codes

Official

F45.20Hypochondriacal disorder, unspecified

F45.22Body dysmorphic disorder

F45.29Other hypochondriacal disorders

Includes

Official

ICD-10-CM does not list Includes notes for F45.21 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for F45.21 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for F45.21 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for F45.21 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for F45.21 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documented persistent conviction or fear of having a serious medical disease

Record of repeated medical evaluations failing to confirm the feared condition

Evidence that reassurance from providers does not alleviate the preoccupation

Duration of preoccupation for at least six months

MEAT Support

HCC Buddy guidance

Documented persistent conviction or fear of having a serious medical disease

Record of repeated medical evaluations failing to confirm the feared condition

Evidence that reassurance from providers does not alleviate the preoccupation

Duration of preoccupation for at least six months

Audit Caution

HCC Buddy guidance

Coding hypochondriasis when the patient actually has a medical condition causing legitimate concern

Confusing hypochondriasis with somatic type delusional disorder — the distinction lies in whether the belief is delusional vs. anxious preoccupation

Using the unspecified F45.20 when documentation clearly supports the specific F45.21

Failing to capture comorbid depression or anxiety disorders commonly associated with hypochondriasis

Common Mistakes

HCC Buddy guidance

F45.20 (Hypochondriacal disorder, unspecified) — use F45.21 when classic hypochondriasis is specifically documented

F45.0 (Somatization disorder) — prominent somatic symptoms across organ systems, not just illness fear

F22 (Delusional disorder) — somatic type delusion is fixed and bizarre; hypochondriasis involves worry, not true delusion

F41.1 (Generalized anxiety disorder) — broader anxiety, not specifically illness-focused

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is F45.21 an HCC code?

F45.21 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.

HCC Category Mapping

RxHCCHCC 133, Personality Disorders, Anxiety, and Other Specified Mental Disorders

0.035

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 F45.21 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for F45.21

For F45.21to 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 F45.21 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

F45.21 is the ICD-10-CM diagnosis code for hypochondriasis. An excessive and persistent worry about having a serious disease or illness, often accompanied by frequent health-related behaviors like checking for symptoms or seeking reassurance. F45.21 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).

F45.21 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 F45.21 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 F45.21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Distinguish from health anxiety by documenting the preoccupation with having disease rather than fear of getting it
•Note that reassurance-seeking and body checking behaviors are common features

Clinical Significance

Hypochondriasis is the specific form of illness anxiety disorder characterized by persistent conviction of having a serious, undiagnosed disease despite repeated negative medical evaluations. These patients generate significant healthcare costs through repeated testing and specialist visits. Accurate coding facilitates appropriate psychiatric referral and cognitive behavioral therapy interventions.

Documentation Requirements

✓Documented persistent conviction or fear of having a serious medical disease
✓Record of repeated medical evaluations failing to confirm the feared condition
✓Evidence that reassurance from providers does not alleviate the preoccupation
✓Duration of preoccupation for at least six months
✓Functional impairment or marked distress from the illness preoccupation

Commonly Confused Codes

•F45.20 (Hypochondriacal disorder, unspecified): use F45.21 when classic hypochondriasis is specifically documented
•F45.0 (Somatization disorder): prominent somatic symptoms across organ systems, not just illness fear
•F22 (Delusional disorder): somatic type delusion is fixed and bizarre; hypochondriasis involves worry, not true delusion
•F41.1 (Generalized anxiety disorder): broader anxiety, not specifically illness-focused
•F45.22 (Body dysmorphic disorder): preoccupation with appearance/defect, not disease