Biolgy books, my mom who is a nurse, and biolgy class I also wanted and still do want to be a doctor You can get it online if you want 14 is high but 15,16,17,18 is higher up in to the early 20's http://homepage.psy.utexas.edu/homepage/faculty/josephs/pdf_documents/Testos_Encyclo_Entry.pdf Page 2, 4th parghoarht after "Adulthood section" http://www.criticalbench.com/normal-testosterone-levels.htm