The patient presents with a concerning pattern of substance use, meeting the criteria for Substance Use Disorder Unspecified (DSM-5 305.90, ICD-10 F19.90).  The patient acknowledges problematic substance use resulting in clinically significant impairment or distress, but the specific substance or combination of substances used could not be reliably determined at this time.  Symptoms consistent with substance use include reported mood swings, interpersonal difficulties, and periods of impaired judgment.  The patient denies specific substance use when questioned, exhibiting a lack of insight or potential minimization of the problem.  Further investigation is required to identify the specific substance(s) involved. Differential diagnoses considered include other mental health disorders that can mimic substance use, such as bipolar disorder and anxiety disorders.  The patient will be referred for a comprehensive substance use evaluation, including laboratory testing, to determine the specific substances used and develop a targeted treatment plan.  Initial treatment recommendations focus on psychoeducation regarding substance use disorders, motivational interviewing to enhance readiness for change, and connection to community resources for support.  Medical necessity for continued care is established based on the patient's functional impairment and the need for further diagnostic clarification.  The prognosis is guarded until the specific substance(s) of abuse are identified and a tailored treatment plan implemented.  Continued monitoring and reassessment will be necessary to track progress and adjust interventions as needed.