A 52-year-old Caucasian woman presents to her PCP with complaints of increasing fatigue and weakness over the past 3 to 4 months. She is an avid runner and finds it difficult to keep her usual distance or pace. She tried adding a multivitamin to her daily regimen and has been tracking her sleep on an exercise-tracking watch for the past month without significant findings. She does report having some irregularity with her menses over this past year, but her routine gynecologic exam showed no significant concerns and she denies excessive or heavy bleeding. Her gynecologist reportedly told her she is likely in perimenopause after confirming she is not pregnant with an in-office urine hCG, and she has a follow-up appointment scheduled in about 6 weeks. The patient denies any anxiety or depression and reports good social activity. Her diet is vegetarian and reported as well balanced.