F31.81·ICD-10-CM

Bipolar II Disorder

At least one hypomanic episode and at least one major depressive episode, without any history of a full manic episode. Distinct from Bipolar I; not a milder version.

Recommended screener

Validated screener
Mood Disorder Questionnaire (MDQ)
View scale

DSM-5-TR diagnostic criteria summary

Bipolar II Disorder requires:

  • At least one hypomanic episode:
  • Distinct period of elevated, expansive, or irritable mood AND increased activity/energy lasting **at least 4 days**
    • Three or more (4 if mood only irritable) of: inflated self-esteem, decreased need for sleep, pressured speech, flight of ideas, distractibility, increased goal-directed activity, excessive risk-taking
    • Unequivocal change from baseline observable by others
    • NOT severe enough to cause marked impairment, hospitalization, or psychotic features
    • No history of a manic episode. If full mania has ever occurred, the diagnosis is Bipolar I (F31.x).
    • The depression and hypomania are not better explained by schizoaffective disorder or other psychotic disorders.
    • Symptoms cause clinically significant distress or impairment, typically during depressive episodes.

    Source: American Psychiatric Association. (2022). Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR), p. 157–168.

    Differential diagnosis

    • F31.1 Bipolar I Disorder, when any lifetime full manic episode (7+ days, marked impairment, psychotic features, or hospitalization) is identified.
    • F33.x Major Depressive Disorder, when no lifetime hypomanic or manic episode is identified. Subtle hypomania often missed without targeted screening.
    • F60.3 Borderline Personality Disorder, affective shifts in BPD are brief (hours-to-days) and reactive to interpersonal triggers; Bipolar II hypomania is sustained mood elevation lasting days-to-weeks.
    • F34.0 Cyclothymic Disorder, chronic mood instability with hypomanic and depressive symptoms that don't meet full episode criteria.
    • Substance/Medication-Induced Bipolar (F19.x), stimulants, corticosteroids; antidepressant-induced hypomania persisting beyond pharmacologic effect remains coded as bipolar.

    Common comorbidities

    Bipolar II has very high lifetime comorbidity. Common co-occurring conditions: Generalized Anxiety Disorder (F41.1), Panic Disorder (F41.0), Substance Use Disorders (F10–F19, especially alcohol), ADHD (F90.x), Eating Disorders (F50.x), and Borderline Personality Disorder (F60.3, particularly common, ~20% comorbidity). Co-administer PHQ-9, GAD-7, AUDIT, and (where indicated) ASRS alongside the MDQ.

    Sources

    • American Psychiatric Association. (2022). Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR), F31.81, p. 157–168.
    • Hirschfeld, R. M., et al. (2000). Development and validation of the Mood Disorder Questionnaire. American Journal of Psychiatry, 157(11), 1873–1875.
    • Centers for Disease Control and Prevention. ICD-10-CM Official Coding Guidelines.

    Frequently asked questions

    What is ICD-11 code F31.81?

    F31.81 is the ICD-11-CM code for Bipolar II Disorder, characterized by at least one hypomanic episode and at least one major depressive episode, without any history of a full manic episode. It is distinct from Bipolar I (F31.x) which requires lifetime mania.

    What are the diagnostic criteria for F31.81?

    DSM-5-TR Bipolar II requires: at least one hypomanic episode (4+ days of elevated/irritable mood plus 3 or more symptoms, inflated self-esteem, decreased sleep need, pressured speech, racing thoughts, distractibility, increased activity, risky behavior, without psychotic features and not requiring hospitalization); at least one major depressive episode; no history of a manic episode; symptoms cause clinically significant distress or impairment in social/occupational functioning typically during depressive episodes.

    What is the difference between Bipolar I (F31.x) and Bipolar II (F31.81)?

    Bipolar I requires at least one full manic episode in lifetime, characterized by 7+ days of elevated mood with marked impairment, possible psychotic features, often hospitalization. Bipolar II requires hypomanic episodes (4+ days, less impairment, no psychotic features, no hospitalization) plus major depressive episodes. Bipolar II is NOT a milder version of Bipolar I, depressive episodes are often more severe and chronic than in Bipolar I.

    What scale is used to screen for F31.81?

    The Mood Disorder Questionnaire (MDQ) is the most widely-used bipolar spectrum screener. It is somewhat less sensitive for Bipolar II (~58%) than Bipolar I (~73%) due to the subtler hypomanic presentation. The Hypomania Checklist (HCL-32) is more sensitive for Bipolar II and bipolar spectrum but less widely deployed.

    Why is Bipolar II often misdiagnosed?

    Patients typically seek help during depressive episodes; hypomanic episodes often go unreported because they feel normal or pleasant. Without targeted screening (MDQ, HCL-32) before initiating antidepressant therapy, Bipolar II is frequently misdiagnosed as recurrent depression. Antidepressant monotherapy in unrecognized Bipolar II carries risk of induced mania or rapid cycling. Routine MDQ screening before antidepressant initiation reduces this risk.

    Is F31.81 a billable ICD-11-CM code?

    Yes, F31.81 is a billable ICD-11-CM code as of the 2025 official tabular list. It is the standard reimbursed code for Bipolar II Disorder. Bipolar II uses a single code rather than the multi-character episode specifiers used for Bipolar I (F31.0 through F31.5); current episode (depressed vs hypomanic) is captured in clinical documentation rather than the code itself.

    What are the symptoms of bipolar II disorder?

    Bipolar II Disorder alternates between depressive episodes and hypomanic episodes. Depressive symptoms include low mood, loss of interest, fatigue, sleep changes, worthlessness, and concentration problems lasting at least two weeks. Hypomanic symptoms include elevated or irritable mood, decreased need for sleep, racing thoughts, increased activity, and risky behavior lasting at least four days. Hypomania is noticeable to others but does not cause marked impairment or require hospitalization.

    How is bipolar II disorder diagnosed?

    Bipolar II Disorder is diagnosed by a clinician using DSM-5-TR criteria, which require at least one lifetime hypomanic episode plus at least one major depressive episode, with no history of full mania. Diagnosis typically follows a positive MDQ or HCL-32 screen, structured clinical interview, collateral history, and a longitudinal mood chart. Patients usually present during depression, so targeted hypomania screening is essential.

    What causes bipolar II disorder?

    Bipolar II Disorder arises from genetic, neurobiological, and environmental factors. Heritability estimates from twin and family studies range from 60% to 80%. Neurobiological contributors include altered serotonin, dopamine, and glutamate signaling, plus circadian rhythm dysregulation. Triggers for episodes include sleep deprivation, major life stress, substance use, postpartum hormonal shifts, and antidepressant exposure in genetically vulnerable individuals.

    Can bipolar II disorder be cured?

    Bipolar II Disorder is a chronic, lifelong condition managed with sustained treatment rather than cured. First-line treatment combines mood stabilizers (lithium, lamotrigine, quetiapine) with structured psychotherapy such as CBT, IPSRT, or family-focused therapy. With consistent maintenance treatment, many people achieve long periods of stable mood; depressive episodes are typically more frequent and disabling than hypomanic episodes and require ongoing monitoring.

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