ICD-11
According to the ICD-11, a BP-II patient will have experienced episodic experiences of one or more hypomaniac episodes and one or more major depressive episodes, and no history of a manic episode or mixed episode. These symptoms cannot be explained by other diagnoses such as

Cyclothymia
ADHD
Oppositional Defiant Disorder
Schizophrenia and other primary psychotic disorders
Substance-Use Disorder
Personality Disorders
Other Mental illness
Physical issues such as a brain tumorThe specifiers are the same as the DSM-5 with the exception of catatonic features and if symptoms have occurred with or without psychosis about 6 weeks after childbirth

Differential diagnoses
The signs and symptoms of BP-II may overlap significantly with those of other conditions. Thus, a comprehensive history, medication review, and laboratory work are key to diagnosing BP-II and differentiating it from other conditions. The differential diagnosis of BP-II is as follows: unipolar major depression, borderline personality disorder, posttraumatic stress disorder, substance use disorders, and attention deficit hyperactivity disorder. : 1653–7  In clinical practice, the difficulty of diagnosing BP-II depends on the accurate detection of hypomania, which is frequently dismissed by patients. Patients can present with increased productivity and energy with the absence of signs of instability or disturbance. As such, there is a risk that BP-II is misdiagnosed as generalized anxiety disorder or unipolar major depression. An accurate evaluation of differential diagnoses are crucial, as they guide treatment and prognostic implications.Major differences between BP-I and BP-II have been identified in their clinical features, comorbidity rates and family histories.
In patients with comorbid substance use disorder and BP-II, episodes have a longer duration and treatment compliance decreases. Preliminary studies suggest that comorbid substance use is also linked to increased risk of suicidality. Diagnosis
BP-II is diagnosed according to the criteria established in the American Psychiatric Associations Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). In addition, alternative diagnostic criteria is established in the World Health Organizations International Classification of Diseases-10th Revision (ICD-10). The diagnostic criteria are established from self-reported experiences from patients or their family members, the psychiatric assessment, and the mental status examination. In addition, Screening instruments like the Mood Disorders Questionnaire are helpful tools in determining a patients status on the bipolar spectrum. In addition, certain features have been shown to increase the chances that depressed patients have a bipolar disorder, including atypical symptoms of depression like hypersomnia and hyperphagia, a family history of bipolar disorder, medication-induced hypomania, recurrent or psychotic depression, antidepressant refractory depression, and early or postpartum depression. DSM-5 criteria
According to the DSM-5, a patient diagnosed with BP-II will have experienced at least one hypomanic episode, at least one major depressive episodes, and no manic episode. Furthermore, the occurrence of the mood episodes are not better explained by schizoaffective disorder, schizophrenia, delusional disorder, or other specified or unspecified schizophrenia spectrum and other psychotic disorder.