What is ICD-10 code F31.31?

F31.31 is the ICD-10-CM diagnosis code for Bipolar disorder, current episode depressed, mild. Bipolar disorder with a current mild depressive episode, where the person experiences depressed mood and loss of interest with minimal impact on daily functioning. F31.31 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. F31.31 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. F31.31 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. F31.31 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.

Which HCC does F31.31 map to under V28?

F31.31 maps to CMS-HCC V28 HCC 154 (Bipolar Disorders without Psychosis). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM F31.31: Bipolar disorder, current

F31.31 maps to CMS-HCC V28 154. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software

ICD-10-CM Code View

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Code lookupF31.31

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Mental, Behavioral and Neurodevelopmental disorders (F01-F99) / Mood [affective] disorders (F30-F39)

F31.31

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

Bipolar disorder, current episode depressed, mild

Bipolar disorder with a current mild depressive episode, where the person experiences depressed mood and loss of interest with minimal impact on daily functioning.

Buddy Insight

Bipolar disorder with current mild depressive episode indicates the patient is experiencing low-grade depressive symptoms within the context of their bipolar illness.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 154

Bipolar Disorders without Psy...

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

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 131

Bipolar Disorders

Code-level coefficient reference

Code Book Path

Official

F31Bipolar disorder F31.3Bipolar disorder, current episode depressed, mild or moderate severity F31.31Bipolar disorder, current episode depressed, mild

Inclusion Terms

Official

No inclusion terms are included in this display for F31.31. Check the code and parent instructions in the Code Book.

Excludes 2

Official

symptoms, signs and abnormal clinical laboratory findings, not elsewhere classified (R00-R99)Inherited from F01-F99, F31
cyclothymia (F34.0)Inherited from F01-F99, F31

Related Codes

Official

F31.30Bipolar disorder, current episode depressed, mild or moderate severity, unspecified F31.32Bipolar disorder, current episode depressed, moderate

Includes

Official

disorders of psychological developmentInherited from F01-F99, F31
bipolar I disorderInherited from F01-F99, F31
bipolar type I disorderInherited from F01-F99, F31
manic-depressive illnessInherited from F01-F99, F31
manic-depressive psychosisInherited from F01-F99, F31
manic-depressive reactionInherited from F01-F99, F31
seasonal bipolar disorderInherited from F01-F99, F31

Excludes 1

Official

bipolar disorder, single manic episode (F30.-)Inherited from F31
major depressive disorder, single episode (F32.-)Inherited from F31
major depressive disorder, recurrent (F33.-)Inherited from F31

Code First

Official

No Code First sequencing instructions are included in this display for F31.31. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for F31.31. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for F31.31. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Documented bipolar disorder diagnosis with history of manic or hypomanic episodes

Current depressive symptoms explicitly described as mild

Functional assessment showing minimal but present impairment

Absence of psychotic features

MEAT Support

HCC Buddy guidance

Documented bipolar disorder diagnosis with history of manic or hypomanic episodes

Current depressive symptoms explicitly described as mild

Functional assessment showing minimal but present impairment

Absence of psychotic features

Audit Caution

HCC Buddy guidance

Defaulting to unspecified severity (F31.30) when the provider documents mild

Confusing bipolar depression with unipolar depression and assigning F32.0

Using this code for adjustment disorder with depressed mood when bipolar criteria are not met

Missing provider documentation of 'stable bipolar, mild depressive symptoms' as a codeable current episode

Common Mistakes

HCC Buddy guidance

F31.30 — Bipolar disorder, depressed, mild or moderate unspecified: Use F31.31 when mild is specifically documented

F31.32 — Bipolar disorder, depressed, moderate: Greater functional impairment than mild

F32.0 — Major depressive disorder, single episode, mild: No bipolar history

F34.1 — Dysthymic disorder: Chronic low-grade depression without bipolar cycling

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 F31.31 an HCC code?

Yes. F31.31 (Bipolar disorder, current episode depressed, mild) maps to HCC 154, Bipolar Disorders without Psychosis under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.351. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: F31.31 is billable and maps to V28 HCC 154, Bipolar Disorders without Psychosis. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: F31.31
Description: Bipolar disorder, current episode depressed, mild
HCC (V28): HCC 154 — Bipolar Disorders without Psychosis
RAF reference coefficient: 0.351
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 154, Bipolar Disorders without Psychosis

0.351

RxHCCHCC 131, Bipolar Disorders

Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work F31.31 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for F31.31

For F31.31, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

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

Coder workflow notes

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What This Code Means

F31.31 is the ICD-10-CM diagnosis code for bipolar disorder, current episode depressed, mild. Bipolar disorder with a current mild depressive episode, where the person experiences depressed mood and loss of interest with minimal impact on daily functioning. F31.31 sits in the ICD-10-CM chapter for mental, behavioral and neurodevelopmental disorders (f01-f99), within the section covering mood [affective] disorders (f30-f39).

Under the CMS-HCC V28 risk adjustment model, F31.31 maps to Bipolar Disorders without Psychosis (HCC 154) with a source-labeled community, non-dual, aged reference coefficient of 0.351. No V24 mapping is shown for F31.31; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Mild severity indicates the depressive symptoms cause minimal impairment in social, occupational, or other important areas. For F31.31, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for F31.31 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Mild severity indicates the depressive symptoms cause minimal impairment in social, occupational, or other important areas
•Document specific depressive symptoms and the level of functional impairment to support the mild severity designation

Clinical Significance

Bipolar disorder with current mild depressive episode indicates the patient is experiencing low-grade depressive symptoms within the context of their bipolar illness. While mild, this state requires monitoring for worsening and careful medication management to prevent both deepening depression and medication-induced mania. Capturing this accurately supports continuity of psychiatric care.

Documentation Requirements

✓Documented bipolar disorder diagnosis with history of manic or hypomanic episodes
✓Current depressive symptoms explicitly described as mild
✓Functional assessment showing minimal but present impairment
✓Absence of psychotic features
✓Current medication management plan

Commonly Confused Codes

•F31.30: Bipolar disorder, depressed, mild or moderate unspecified: Use F31.31 when mild is specifically documented
•F31.32: Bipolar disorder, depressed, moderate: Greater functional impairment than mild
•F32.0: Major depressive disorder, single episode, mild: No bipolar history
•F34.1: Dysthymic disorder: Chronic low-grade depression without bipolar cycling