Study Design Subjects will be recruited from an outpatient population of subjects with psoriasis from Dr. Jennifer Soung's clinic at the Gottschalk Medical Plaza at the University of California, Irvine. Subjects with the requisite diagnosis of psoriasis who are starting a new form of therapy will be candidates for enrollment. Subjects who choose not to participate in the study will receive their standard of care treatment without any monitoring for vitamin D level. The protocol for this study is as follows. Subjects will be screened and consented. Upon entry into the study, the study subject's severity of disease will be evaluated by the investigator, using the Psoriasis Area and Severity Index (PASI), Body Surface Area (BSA), and Physician's Global Assessment (PGA). These assessments will be repeated at all future study visits. Subjects will receive whichever standard of care treatment for their psoriasis as if they were not participating in this study