2026 ICD-10-CM Diagnosis Code F31.31Bipolar disorder, current episode depressed, mild

ICD-10-CM Codes›F01–F99›F30-F39›F31

ICD-10-CM F31.31
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

F31.31 is a billable ICD-10-CM diagnosis code for bipolar disorder, current episode depressed, mild. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). Coders also document this condition as bipolar affective disorder, current episode depression. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bipolar and related disorders.

Code Identity

ICD-10-CM Code
F31.31
Billable Status
Yes — Valid for Submission
Code Describes
Bipolar disorder, current episode depressed, mild
Short Description
Bipolar disorder, current episode depressed, mild
Same as the full description in the CMS dataset.
Parent Code
F31.3
Bipolar disorder, current episode depressed, mild or moderate severity

Code Classification

ChapterF01–F99Mental and behavioural disorders
SectionF30-F39Mood [affective] disorders
CategoryF31Bipolar disorder
This CodeF31.31Bipolar disorder, current episode depressed, mild

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Bipolar affective disorder, current episode depression
  • Bipolar affective disorder, currently depressed, mild
  • Depressed bipolar I disorder
  • Mild bipolar disorder
  • Mild depressed bipolar I disorder

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Disorder(of)
      • bipolar (I) (seasonal) (type 1)
        • current (or most recent) episode
          • depressed
            • without psychotic features
              • mild

Clinical ClassificationClinical

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

CCSR MBD003
Bipolar and related disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Bipolar Disorder

Bipolar disorder is a mood disorder that can cause intense mood swings:

The full article covers:

  • What is bipolar disorder?
  • What are the types of bipolar disorder?
  • What causes bipolar disorder?
  • Who is at risk for bipolar disorder?
  • What are the symptoms of bipolar disorder?
  • How is bipolar disorder diagnosed?
  • What are the treatments for bipolar disorder?

Read the full article at MedlinePlus

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

Convert F31.31 to ICD-9-CMHistory

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

ICD-9-CM
296.51 Bipol I cur depress-mild
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About F31.31Overview

Is F31.31 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report bipolar disorder, current episode depressed, mild on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What is the ICD-9 equivalent of F31.31?

Under the General Equivalence Mappings, bipolar disorder, current episode depressed, mild converts to ICD-9-CM 296.51 (bipol I cur depress-mild). The mapping is a direct match.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.